The 'Battle of the Ypres-Comines Canal' was fought between German and British forces in the course of the retreat of General the Lord Gort’s British Expeditionary Force toward Dunkirk, whence it was to be evacuated in 'Dynamo' (26/28 May 1940).

Part of the 'Battle of Belgium' and the considerably larger 'Battle of France', the 'Battle of the Ypres-Comines Canal' began during the afternoon of 26 May and reached its greatest intensity on 27 and 28 May. The origins of the battle can be found in the 23 May decision of Generaloberst Gerd von Rundstedt, commander of Heeresgruppe 'A', to halt his armoured forces, a 'halt order' which was later confirmed by Adolf Hitler. The responsibility for attacking the British, French and Belgian forces trapped in the pocket formed by the advance of Heeresgruppe 'A' toward the southern coast of the English Channel, now lay with Generaloberst Fedor von Bock’s Heeresgruppe 'B' on the Allied forces' eastern front.

On 24 May, Heeresgruppe 'B' launched an attack on the Belgian forces stationed along the Lys river to the east of Menin. This attack achieved rapid success and, as a result, Heeresgruppe 'B' conceived the idea of changing the direction of its attack from the north-west to the west in order to prevent the British and French forces in the pocket from reaching the coast. Orders to that effect were issued by Generaloberst Walter von Reichenau, commander of the 6^th Army, at 23.30 on 24 May. By the following day, the Belgian armies were retreating in a northerly direction and a gap was opening between them and the British in the area to the north of the Lys river. This offered the German forces the space they needed to effect their planned change of direction. Gort had intended to take part in a French-led attack to the south with the object of bridging the gap between the Allied forces in the pocket and the main French forces farther to the south. By the middle of the afternoon of 25 May, however, information was reaching Gort about the Belgian collapse and the consequent threat to his north-eastern front, and at about 18.00 Gort decided that Major General H. C. Franklyn’s 5^th Division, which was to have participated in the attack to the south, should instead go north in order to defend the Ypres-Comines Canal running between those two towns.

During 25 May, the 6^th Army's orders of the previous day, concerning the attack to the west, were captured by a British unit and were delivered to Gort. It has often been said that this capture caused Gort to take his decision, but it seems clear that he had, in fact, already taken it before he was shown the captured orders.

The 5^th Division, comprising Brigadier M. C. Dempsey’s 13^th Brigade and Brigadier M. G. N. Stopford’s 17^th Brigade augmented by Brigadier J. Muirhead’s 143^rd Brigade from Major General R. L. Petre’s 48^th Division, took up position on the canal during 26 May. During the following battle, the 5^th Division was part of the British II Corps commanded by Lieutenant General A. F. Brooke. Major General G. Le Q. Martel’s 50^th Division was also sent to Ypres on 26 May, arriving during the night of 26/27 May, but this formation played only relatively small part in the battle, which took place mainly to the south of the town. British troops came across a few Belgian engineers who were preparing bridges on the western part of Ypres for demolition. The German formation involved was General Viktor von Schwedler’s IV Corps, and comprised Generalleutnant Friedrich-Carl Cranz’s 18^th Division, Generalleutnant Rudolf Kaempfe’s 31^st Division and Generalleutnant Siegfried Hänicke’s 61^st Division. The Germans, therefore, started with a considerable superiority in numbers although this was reduced as British reinforcements were fed into the battle.

The Germans started probing attacks on the afternoon of 26 May and launched a full-scale attack on the morning of the following day. By the middle of the afternoon, the British line had been forced back, with German penetrations of more than 1 mile (1.6 km) in the south and north. From a time late in the afternoon the British launched a series of counterattacks. Units involved included the 2/Cameronians (Scottish Rifles) of the 13^th Brigade in the centre, and the 6/Black Watch (Royal Highland Regiment), 13^th/18^th Royal Hussars, 1/7^th & 8^th Royal Warwickshire Regiment and Royal Engineers units farther to the south. Later, another counterattack in the south was launched by the 2/North Staffordshire Regiment and 3/Grenadier Guards, borrowed by Brooke from Major General E. L. Morris’s 1^st Division. As a result, the 31^st Division's attack in the centre was halted while the 61^st Division in the south was driven back almost to the canal. In the north, however, the 18^th Division continued to advance on the southern side of Ypres. On 28 May, the German advance resumed, but made little progress in the centre and south. Some farther advances were made in the north, but Brooke had switched Brigadier E. H. Barker’s 10^th Brigade from Major General T. R. Eastwood’s 4^th Division, and this stabilised the front.

Throughout the battle the British artillery, the equivalent of six field artillery regiments and five medium and heavy regiments, and was stationed primarily on the Messines-Wytschaete Ridge, had done much to break up the various German attacks. Because of this, the British probably had a larger artillery presence than the Germans, and contributed to the British defence.

During the night of 27/28 May, most of the British forces south of the Lys river, four divisions in all, crossed and made their way to the north. The 5^th and 50^th Divisions pulled out on the night of 28/29 May. The 5^th Division’s stand had been critical in allowing a substantial part of the British Expeditionary Force’s fighting strength to reach Dunkirk. Therefore, although total British casualties, including men taken prisoner, exceeded those of the Germans, the battle was an important British success. Much of this was attributable to Brooke’s prompt actions. During 27 May, he borrowed the Guards and North Staffords, who participated in the second counterattack in the south, from the 1^st Division, and moved the 10^th Brigade to reinforce the centre and north.