Third Battle of Ypres Part 3: Passchendaele - the Pyrrhic victory

The liberated rubble of the church at
Passchendaele November 1917

Repeatedly in this blog I have been critical of British C-in-C Sir Douglas Haig or, at best, been unsympathetic to the enormous responsibility he held with little or no opportunity to pass the buck. But he had a hellish job that few people would have wanted to take on. As his senior Generals Plumer and Gough pleaded with him to stop, or at least suspend, the bloodbath in the Ypres mire, he must surely have thought it the path of least resistance. He knew his favoured strategic breakthrough to the Belgian coast was lost, but he had to weigh this against keeping the Germans as fully occupied in Flanders as possible, while Petain’s main French forces recovered in Artois for another sally on the Aisne heights; and his own 3^rd Army, under Byng, prepared for a tank led breakthrough attempt at Cambrai. The scale of casualties in his forces to date had been worse than at the Somme, and the state and morale of Gough’s 5^th army were both of serious concern. He knew men had been withdrawn from the Belgian coast in favour of Italy (by an unsupportive Prime Minister), and that further men would need to be moved from Flanders to support the Cambrai action. Somehow he had to persuade Gough and Plumer to convince their own men to continue towards what could now be no more than a tactical victory to control the heights of the Ypres salient. Seemingly, he did not waver.

Buchan describes the last stages of Ypres 3 as the “muddiest combats known in the history of war” – as if it hadn’t been bad enough already. Haig’s concession to the combined appeal of Gough, Plumer and all their senior officers was to order Currie’s Canadian Corps, further south, to come under Plumer’s command and become the spearhead for the ‘final push’ to Passchendaele. Their commander Lt. General Currie was a tough competitor – the Dominion of Canada’s first great military hero. His men were still relatively fresh, having recently captured Hill 70 near Lens as part of Byng’s diversionary action (see post 31/7/2017). Currie was not in a position to defy Haig’s order to move his men to Flanders, but he did refuse to let them loose on the morass of the Passchendaele ridge until his full preparations had been made – causing further unwanted delay for Haig.

Overall, in the final month of Ypres 3 the scale of fighting was much less than in the earlier phases. The main thrust to the village from the west would be entrusted to the Canadians. To the south the ANZACs (2^nd Army) pushed on through Zonnebeeke to the vanished hamlet of Nieuwvemolen. To the north the British Guards, the Royal Naval Division (both 5^th Army|) and the French 1^st army progressed eastwards – the British taking Poelkapelle and beyond; and the French doing even better, penetrating the large Houthulst forest north east of Langemarck. These advances on the flanks were important in preventing artillery and enfilade attacks against the eventual Canadian advance.

Arthur Currie: a stalwart leader of his
countrymen at Ypres 2 and 3

Currie’s plan was that, if the weather was tolerable and every available man would support his preparations, he would be ready to move in late October. Plumer gave his backing to this, shielding Currie from Haig’s impatience. In the interim some futile attempts on the broader front were continued by Gough’s 5^th army, from Polygon Wood to Langemarck. Incremental gains were made on October 8^th and 9^th, but further torrential rain on 11^th precluded any further progress. Even a day or two with no rain made no difference in some flooded areas. One observer wrote “You might as well try to empty a bath by holding lighted matches over it”*.

On 25^th October, helped slightly by a strong following wind that at least dried out the surface mud on the slopes, the Canadian infantry began to move up the line. Early on 26^th they attacked toward the hillock south of Passchendaele, aided by the flanking activities described above. Their objective was carried by the early afternoon. On their right flank the British entered Gheluvelt for the first time since the initial battle for Ypres in late 1914. Further progress to Passchendaele was held up for two days in fierce fighting for a shattered piece of woodland, aptly named Decline Copse. The Canadians and Australians both ended up attacking this stronghold, and eventually took it, but with heavy casualties.

The final assault on Passchendaele itself began on 30^th October. The Canadians took Crest Farm on the southern edge of the village (site of the memorial today), but the Naval Division on their left could not advance across the treacherous hinterland to join and strengthen them. Again, Currie insisted on a further pause for reinforcements for his men before the final 200metres advance to the centre of the village. This duly happened on 6^th November, when the bolstered Canadian 1^st and 2^nd Divisions swept past the ruins of the church and beyond the village to the Goudberg spur. A final attack on 10^th November secured this spur and marked the official end to the terrible Third Battle of Ypres.

Haig had reached his target, 99 days after the 31^st July jump-off from his starting line 5miles to the west. It was five months since the drama at Messines Ridge, and more than half a million men from both sides had died, been injured or disappeared in the mud. Haig had his momentary tactical victory and another strategic failure.

Passchendaele Church, rebuilt on the rubble.
A moving tribute to events of 1917

By any standards – and Buchan does his best to offer a patriotic rose coloured hue to the outcomes – the capture of Passchendaele was a Pyrrhic victory, like the Somme. Accurate casualty figure are still elusive, 100 years on, but it seems likely they were in excess of 350,000 for both sides. Undoubtedly, the Germans suffered terribly (as they did eventually at the Somme), but Gough’s brave 5^th Army was all but broken by the ghastly attritional mud-churn of the battle.

Before the end, whole divisions were being moved to France, for Cambrai, and to Italy to support the strategic opportunity there. At least (it might be said) the British now controlled all the high ground around the Ypres salient for the first time since 1914. But the final insanity of Ypres 3 came within a few months, as all the ground won in those five months of battles was ceded without contest in the great German Spring offensive of 1918. The Ypres salient would be reduced to the remains of the town and its outskirts. This was just the line proposed in 1915 by the unsung General Horace Smith-Dorrien after the gas attacks of Ypres 2.  HS-D was sacked for his temerity. Perhaps he should have been promoted over Haig?

* Buchan J. A History of the Great War Volume 3 p599

Third Battle of Ypres - Part 2: August and September

A familiar image of the horrors of Passchendaele

The biblical rains of early August transformed an already churned and bleak landscape to a morass of glutinous mud. For men holding the front lines, existence was sheer misery - in many places with hundreds of corpses strewn about their immediate vicinity. For those charged with supplying and reinforcing the front line the prospect was just as unattractive. The German artillery still overlooked most positions including the main route from Ypres - the Menin Rd. The routes themselves were dangerously flooded. Duckboards picked out hazardous pathways for men, horses and equipment but heavy losses of all three groups occurred in the mud and howling rains.
Rawlinson's army had now taken up position, replacing the Belgian contingent at Nieuport on the coast. They were ready to join the planned amphibious assault on the U-boat bases at Ostend and Zeebrugge when the signal was given. However, they needed Haig's forces to make the breakthrough behind the German lines and beyond Passchendaele before they could do so. Despite the encouraging progress of 31st July this had from the start been unlikely and, in the presence of the current weather conditions, was rapidly becoming impossible.
With the enforced hiatus, the third battle of Ypres became, in fact, a series of smaller actions focusing on the succession of small ridges leading to the highest point of Passchendaele. Whole divisions were sacrificed through death, injury and exhaustion for the attainment of small tactical objectives. Byng's army at Loos in Northern France started a partially effective diversionary campaign to draw off German reserves, but both sides nevertheless suffered massive casualties over possession of the small, infamously named village of Passchendaele.

Other than consolidating, as best he could, the gains of 31^st July, Gough could do little to meet his commander’s wishes for a breakthrough. He somehow managed to retake the village of St. Julien on 3^rd August, and to improve the position across the Steenbeek stream/torrent in that area, but it was not until mid-August that a few days good weather dried out conditions sufficiently for them to have another serious crack against the line. Gough’s four army corps were pushed forward again on 15^th August against the next tier of ridges en route to Passchendaele, from the Menin Road spur near Gheluvelt north to Langemarck.

Some success was achieved at the northern end, where advances to Langemarck and the hamlet of Wijfvegen were made. Between St. Julien and Frezenberg the German defence, heavily fortified with pillboxes, exacted very heavy casualties on the British attackers. At the southern end, by the Menin Rd, the winding ridges converged on the spur know as Hill 64, close to a hectic and battered crossroads known by the troops as Clapham Junction. Here, progress was difficult, through Inverness Copse and Glencourse Wood towards the large Polygon Wood (all of which were devoid of trees by this time). German defences were strong; heavy artillery overlooked the British communication lines, and losses were high. In the later part of the month heavy rains returned, and by the end of August Gough’s army was exhausted and dispirited, and not yet halfway towards its target.

Most tanks at Ypres 3 ended in a
watery grave

Tanks that had been sent to support the advance were completely inappropriate for the terrain or the conditions, and most were stuck in mud and out of action. Gough reported the difficulties and loss of morale to Haig. Rather than accept the futility of continuing, Haig turned to Plumer’s 2^nd Army to take the heat off Gough’s men.

Plumer employed his customary thoroughness to the planning of what became known as the Battle of Menin Road. Resources, especially artillery, were  built up behind huge screens, and new tactics were developed to deal with the pillboxes problem behind German front lines. Plumer’s aim was to advance a further mile down the Menin Rd past Gheluvelt, to pressure the German positions around Zonnebeeke; and to support and relieve those pushing eastwards from St. Julien and Langemarck/Poelkapelle. September 19^th was set as the day for the next effort, and at dawn the broader advance began. The addition of Plumer’s forces and organisation made a difference and by mid morning all first objectives had been achieved. The formidable Bremen redoubt had been taken, and the outskirts of the town of Zonnebeeke had been reached. Fierce attack and counter attack continued for a week before a new British surge was launched along the same 6 miles stretch. The rest of Zonnebeeke and Polygon Wood were taken – the latter by an Australian division under Plumer’s command. The weather held until early October, and the gains made were consolidated. Exhaustion and the desperate use of reserves were now affecting both sides, and by the time the next phase opened on 3^rd October, so were the returns of gales and lashing rain.

The slow grind to Passchendaele
(Source: Major and Mrs Holt's Battle
Map Ypres Salient and Passchendaele)

The British were aiming for control of the ridge running north from Broodseinde to Graventafel (where Tyne Cot cemetery stands today). On their side, the Germans were aiming to counter attack towards Zonnebeeke.  They had just assembled three fresh divisions in the trenches to go over the top when the British artillery bombardment opened up, causing terrible destruction. They were in complete disarray as the British and ANZAC troops attacked. After another day of severe fighting the British held Poelkapelle; the New Zealanders were in Gravenstafel, and the Australians had taken Broodseinde. Passchendaele was finally in sight.

But the costs were ghastly, and the weather was worsening. On the morning of 7^th October, after a night spent in deep discussion, General Gough and Plumer travelled to Haig’s headquarters and jointly requested that the campaign be halted.  Remarkably (or perhaps not so) Haig refused. He ordered that, in the light of the successes three days earlier, the campaign would continue. His only justification for continuing was tactical. He knew that the strategic breakthrough to the coast to join an amphibious operation against Ostende and Zeebrugge was now impossible. He knew also that Lloyd George had lost interest in the Flanders campaign and was ordering Rawlinson to move men and resources from Nieuport to Italy. Yet again, Haig trotted out that dreadful WW1 phrase “One more push”.

Italy 1917 - Isonzo Battles 10 and 11

The Isonzo Front 1915-1917
(borrowed from the excellent blog 'Things have changed'

Although the Italo-Austrian border snaked for more than 500 miles across the Alps and down to the Adriatic (a distance longer than the Western Front), we have seen in previous posts on Italy (7/7/2015 and 3/11/2016) how the great majority of action occurred along the 60 miles of the River Isonzo front. Only the Austrian gambit from the Trentino region (see Post 3/5/2016) made an incursion into other Italian territory in attempt to cut off the Italian communications to their main front further east. 
The Isonzo front ran from the mountain towns of Plezzo and Bovec in the north down to the Adriatic sea with the river estuary between Montfalcone on the Italian side and the coveted city of Trieste on the Austrian side (see Map). No less than twelve separate battles took place on the Isonzo front from 1915-1917. For the most part they were depressingly 'Groundhog Day' struggles. Following Italian bombardments that grew in intensity with each battle, swathes of infantry would be hurled at Austrian defences that were numerically inferior but strategically placed on mountainous higher ground. Slaughter in these battles was comparable to anything seen on Western and Eastern Fronts. Cadorna, the dominating Italian C-in-C was a good organiser, but his arrogance and pig-headedness resulted in senseless casualties. He sacked hundreds of senior officers for failing to achieve their objectives, or for questioning his tactics. He rarely visited the front, and persisted in his Haig-like belief that one more push would create the breakthrough to open warfare and an advance on Vienna. He treated his troops as fodder, even employing the ancient Roman barbarity of decimation, whereby one in ten troops of a line up post 'failure' were taken out of the line and shot for cowardice in order to stiffen the resolve of the rest. Unbelievable.  
Of the 12 battles, only 6, 11and 12 had strategic impact. The 6th battle resulted in the capture of Gorizia and a toehold on the Carso plain (Post 3/11/2016). The 12th is better known as Caporetto and will be covered separately. Battles 10 and 11 took place in May and August of 1917.

It wasn't as if hostilities ceased and the poor troops got some respite in the winter months. It was that the ferocity of the winter weather - snow, vicious winds, freezing temperatures and avalanches - made mass movements impossible. Men suffered as much (possibly more) as in the major battles, but in localised actions designed to improve defensive positions; create footholds or enhance communications.
In the winter of 1916-17, which saw record snowfalls and dreadful blizzards, both sides made major preparations for the 1917 season of carnage. Boreovic led the Austrian forces in the Isonzo region. Although a Croat rather than Germanic, he was accepted by all as one of Austria's finest generals. Not that that helped his constant appeals for more reserves and equipment. He made the best of his defensive positions lined up, as he was, against greatly superior numbers of Italians. He worked hard to strengthen the new defensive positions he had been forced to take up following the 6th Battle and the loss of Gorizia. Cadorna's larger forces on the front comprised the 2nd Army to the north, led by Capello, and the 3rd Army (south of the Carso plateau to the sea) led by the aristocrat Duke d'Aosta. Capello organised the building of a new road to support the bridgehead east of Gorizia. Cadorna's plan was to blast through beyond this bridgehead, further on to the forbidding Carso plain, drawing the Austrian reserves into that area. Once this was achieved he would launch d'Aosta's 3rd army to take the Monte Hermada heights overlooking the coast and road to Trieste. The town of Kostanjevica was an important target in this move.

Isonzo 10 began on 12th May 1917 with the heaviest bombardment to date, strengthened by British and French artillery. As before, the infantry rush was successful initially. Bridges were constructed across the river, and a broader advance from the Gorizia positions penetrated to the Austrian seond lines 300 metres above the river. In two days Capello's men made incursions into the western end of the Carso and Bainsizza plateaus - physically very different from each other - and both were strategically important. Capello finally took control of Hill 383 (aka Hill of Death to the troops), giving Cadorna a great propaganda prize. So far, so good, despite the predictable counter-attacks from the Austrians that regained some of the lost ground.

Duke d'Aosta - a fine
commander of the 3rd Army

On 23rd May Cadorna ordered phase two, and d'Aosta's 3rd Army swung into action towards Monte Hermada. Supported by over 100 airplanes - an increasing presence in the later battles - they made progress to the foothills and along the coastal marshes but ground to a halt after about two miles. They could not take Kostanjevica.

The 10th battle was judged a success alongside 7, 8 and 9 but all things are relative. The Italian losses for the battle exceeded any other to date. The Austrians also had suffered serious losses, and with their inferior numbers were now stretched very thinly. Boroevic made further appeals to the centre for reinforcements, this time with different and important results. In March 1917, one of the new Emperor Karl's early actions had been to dismiss the vainglorious Austrian Commander in Chief Conrad von Hotzendorf. His replacement was General Arz von Straussenberg, who had considerable experience on the Russian front. He had a constructive relationship with the senior German Military, who had seen Conrad as an irrelevance. Reinforcements that included German equipment were moved from the Russian front and, in early June, strong counter-attacks were launched from the eastern Alpine section of the front, thereby relieving the pressures on Boroevic on the Isonzo. The counter-attacks featured some of the most spectacular and intrepid fighting of the war, involving crack mountain divisions of both sides.
Cadorna's attritional strategy was coming under pressure, not only from these counter-attack on his flank, but from popular and political opinion behind the line. The enormous losses (both sides had lost more than a million men) were sapping the previously strong support for the war. Italy appealed to Britain and France for support in making the 'final' assault across the Carso. Both had major challenges of their own and, despite Lloyd George's enthusiasm to divert from Flanders, could only offer more materiel now, and troops later.
It was, then, with a measure of desperation that Cadorna prepared for what would be his final attempt to lead the breakthrough to the 'road to Vienna'. Whereas Isonzo 10 had focused on two short sections of the front, Isonzo 11 would attack from Plezzo to the sea, seeking for weakness at one of three critical points: Tolmino; Monte San Gabriele, and Monte Herada (see map).
The statutory massive bombardment began on 18th August. By dawn the next day the Italians had secured the river along the whole section and had thrown fourteen bridges across to transport men and equipment. Between Plava and Tolmino two divisions led by General Caviglia scaled the heights of the east bank and made a genuine breakthrough to the Bainsizza plateau. Reinforcements rushed through the gap and in a further three days had taken the ground between Monte Santo and Monte Gabriele. Twenty thousand Austrian prisoners had been taken. Steady but slowing progress was made so that by the twelfth day Cadorna's cavalry was poised to move on to the plateau. But the lengthening supply lines and difficult terrain stymied the cavalry (for the umpteenth time in WW1), and the Austrians held on to sufficient high defensive positions to halt the advance. After a short pause the terrible final phase of Isonzo 11 commenced. Cadorna focused his forces to grind their way along the San Gabriel ridge, a section of about one mile in length, guarding access across the Carso plain and, as a consequence, honeycombed with defensive positions. By 4th September the Italians had taken nearly all of the ridge. Both sides were now desperate. The Austrians rushed in more than thirty battalions to shore up the remaining positions and to launch counter-attacks. The bilateral slaughter continued until mid-September when Cadorna accepted that his famous breakthrough would not be sustained. This phase of the battle had cost over 150,000 casualties, and during 1917 his losses now were approaching three quarters of a million. On the 18th September he informed the Allies that his offensives were at an end.
With heavy irony so typical of WW1 the 11th Battle of the Isonzo reversed the strategy for the two protagonists. Cadorna's armies had been all but smashed on the anvil of mountainous defences, and his own position was precarious. He accepted, at last, the need for defensive positions to hold what he had.

Boreovic - a superb
defensive General

Boroevic, by contrast, now saw that the only chance for his forces (in no better state than the Italians) would be a last chance offensive to force the Italians to retreat. Urgent requests were submitted for German support for such a move.

The French and British leaders failed to appreciate the significance of this shift. Imagining that the Italian front would now go to sleep, they withdrew the reinforcements they had provided reluctantly for battles 10 and 11. In doing so they made their own contributions to one of the Allies biggest defeats in the whole of the war - Caporetto.

Unrestricted submarine warfare 2

The convoy system, belatedly introduced for merchantmen,
averted Britain's looming catastrophe

As recorded in the first part (See Post 16/2/17) the first three months of unrestricted U-boat warfare (UUW) had brought great success to the Germans and induced alarm and crisis activity in Britain. Holzendorff's prescription for the shutting down of Britain's war capability required six months of shipping tonnage at 600,000 tons a month, and the losses for February March and April had averaged more. Perhaps the German optimism was not so fanciful. They had taken the fateful (and ultimately ruinous) decision for UUW in early January. At that point they saw it as the only realistic way for Germany to win outright. They knew about the stretched and exhausted state of their own army, and the low morale and poor physical health of their own population. If they had appreciated fully the parlous state of the Entente powers they might have held off. The French Army was in a worse state than their own; and the Russian effort in the east would shortly cease to exist. The British Empire's resources were keeping the Entente going, but the country itself was on the verge of bankruptcy, and its debts to the USA could not be sustained unless the USA entered the war.  
But now Germany was irrevocably committed to UUW, described by Churchill as ".. one of the most heartshaking episodes of history. It was the greatest conflict ever decided at sea, and almost entirely a duel between Britain and Germany." 

Since their first short period of UUW in 1915, the German strength in U boats had increased greatly. Larger, faster and better armed boats were now capable of making 3-4 weeks patrols. The full complement was now over 150, of which around 70 would be at sea at any one time. Provided the Dover mine barrage could be bypassed (and it could with apparent ease) boats could take the short route from the German and Belgian bases to the vital southern approaches between Ireland and Brittany, and spend 2-3 weeks patrolling in wait for the inbound merchant men. Others took the longer route via the North Sea to patrol the northern approaches round Ireland to the coast of north west England and Scotland.
Once this system was in place, UUW had a rapid and dramatic impact. From a baseline of around 130,000 tons per month in 1916, there had already been a rise late in the year and in January 1917 to more than 250,000 tons sunk. For February the figure was 468,000; for March almost 500,000, and in April it rose to a staggering 869,000 tons. This proved to be the high water mark (sic) for UUW. It still stands as the highest figure ever*. This monthly average actually exceeded Holzendorff's target for strangling Britain in six months, and she was now running out of wheat as well as gold.
Belatedly, the Government and the Admiralty started to get a grip on this dangerous situation. Strenous afforts were made both to improve the protection of merchant shipping and to improve 'seek and destroy' tactics against U-boats. Both were woeful at the start of the year, partly because of the relatively low losses through most of 1916, and the competing pressures for resources to go elsewhere. Arming merchant men to ward off surface attacks from U-boats was the simplest and most obvious measure, but it was a victim of this prioritising - guns were needed everywhere, and only late in 1916 did capacity begin to catch up with demand. In the year 1916 of 600+ merchantmen experiencing surface attack, 76% of those armed escaped, whereas only 22% of those unarmed did so. Q boats (See Post 17/11/2015) were a clever and audacious riposte to surface attacks, although in all of 1915 and 1916 they sunk only 11 U-boats. Perhaps they deterred many more attacks, but by 1917 they were becoming redundant as the Germans were more wary, and were preferring torpedo attacks. Depth charges (still fairly rudimentary) as part of destroyer patrols comprised the other attacking option. There were insufficient destroyers to patrol all of home waters, but at least they were cheaper to build than submarines.
One of Lloyd George's early actions as Prime Minister was to create a new Board of Shipping, merging the offices of Admiralty Chief of Staff and First Sea Lord. Jellicoe was the first holder of this position. The aim was to free up time to focus on improving counter measures. Jellicoe drafted in younger officers to the befuddled Admiralty to deal with this new type of warfare. There were three main areas of focus: better mining; better technology (hydrophones and depth charges); and preparation of convoy plans. The last of these was to be the game changer.
Although convoys had been used for centuries, conventional wisdom held that they were inappropriate for protecting merchant shipping in WW1. This despite the fact that they were in use, successfully, for escorting troopships, and also carrying vital coal supplies across the channel to France**. It was argued that the varying (but slow) speeds and the sheer numbers of merchantmen involved made it too complex an undertaking (wrong). There were insufficient destroyers to protect large numbers of convoys (wrong); and that concentrating ships together would make them an even easier target for U-boats (the reverse proved to be true). Opposition to convoys came from every part of the establishment, the most senior being Jellicoe. Desperation at the position forced a re-think, and production of arguments - mostly from younger officers but also, to his credit, David Beattie, Grand Fleet Commander - to counter the blind logic. Lloyd George and his cabinet were more easily persuade, and prevailed over Jellicoe to insist upon a proper trial. The first experimental convoy left Gibraltar on May 10th 1917, and arrived completely intact. Otherwise overall losses for May remained dangerously high at 600,000 tons. The convoy system was rapidly extended to cover the inbound north and south Atlantic routes. So successful were they over the next three months that the Germans were forced to switch their attacks to un-escorted outbound ships, and gradually these too came under convoy protection (feasible because of the increasing American contributions to destroyer escorts). In October 1917, of 1500 inbound merchant ships only 24 were lost - an astonishing turnaround. Once again the conservative, slow thinking Admiralty had been demonstrably wrong. At Jutland, as Commander of the Grand Fleet, Jellicoe had been prey to this. This time he was the top man at home, but again he shouldered the blame, harshly.

Jellicoe as First Sea Lord.
His disagreement with Lloyd
George cost him his job.

The convoy system all but solved the protection problem and, with increased production from USA involvement, by late 1917 new tonnage far outweighed lost tonnage. The U boat teams were exhausted and many of their best and most audacious leaders had been lost. All possibility of starving Britain to surrender had gone. At the same time the re-invigorated approach to 'seek and destroy' was bearing fruit. Q boats were being replaced by flotillas of submarines that lay in wait for outbound groups of U-boats in the north sea and the channel. The effectiveness of mining tactics improved throughout 1917, particularly in the Channel with the appointment of the dashing Admiral Roger Keys to command of the Dover patrol (see Post 13/9/2015). The previous Dover barrage of 1916 had been ineffective in blocking the Belgian based U-boats from using the Channel route. In the November 1917 reshuffle when Wemyss replaced Jellicoe as First Sea Lord, Keyes replaced Admiral Bacon in the important Dover defensive role. Keyes immediately doubled patrols along the barrier, now laid with the new deep, horned mines, and organised night time illuminations to drive the U boats deeper toward them. This prompted great activity in the Channel, and ultimately closed it off as a route for U-boats.
By early1918, with improving depth charges and listening technology, the U-boats were becoming the hunted rather than the hunters. Britain had ridden out the blockade crisis and the risk of a precipitate defeat.

 * Even Hitler's modern U boat fleets in 1942 at their peak could not match it. 
** France's own coal fields being under German occupation