When the German offensive in the west began on 10 May 1940, nobody on the Allied side thought that the channel ports were in any immediate danger. That all changed after the German breakthrough at Sedan on 14 May, and the dash to the coast that followed. When Guderian’s Panzers reached the mouth of the Somme at Abbeville, German tanks were less than forty miles south of Boulogne. The nearest strong Allied formations were sixty miles to the east, still trying to hold the line east of Lille and preparing for a counterattack, which it was hoped would break through the German lines and restore the situation (Battle of Arras, 21 May 1940).
Luckily for the Allies, the Germans had advanced much faster than they had believed possible, and Guderian’s tanks remained static throughout 21 May, while the High Command decided whether to send them north to capture the channel ports, or south to attack the new French line forming on the Somme. The British used this time well. On the morning of 22 May the 20th Guards Brigade (one battalion each from the Irish and Welsh Guards) was taken to Boulogne by sea, escorted by the destroyers HMS Whitshed and HMS Vimiera. This force was placed under the direct command of General Edmund Ironside, the Chief of the Imperial General Staff, partly because communications between the coast and Lord Gort, the commander of the BEF, were now unreliable. The British found two battalions of French infantry in the town, under the command of General Lanquetot, as well as a number of other troops who had been employed on labour duties behind the front lines and had found their way to the coast. Together the British and French had between 8,000-9,000 men in Boulogne, but the town had not been prepared for defence, and the troops lacked anti-tank weapons – the British had part of one anti-tank battery, the French had a small number of tanks.
On the same day the Germans finally began to move north. II Panzer Division had been given the job of capturing Boulogne. During 22 May they reached the southern part of Boulogne, where they encountered unexpectedly determined resistance. General Walther K. Nehring, Guderian’s chief of staff, rather unfairly believed this to be due to British leadership. The performance of the French garrison over the next few days would suggest that this was not true, but this was certainly the first serious clash between Guderian’s men and the British.
On 23 May II Panzer Division began a much more determined attack on Boulogne. The British had already begun to plan for a possible evacuation and that morning 200 seaman and marines were sent over on the destroyer HMS Vimy, to organise the port. This was a particularly dangerous task, for German troops had reached within small arms range of the harbour area. The danger was clearly illustrated later in the day – the destroyers HMS Keith and HMS Whitshed were sent into the harbour, where Captain D. J. R. Simson of the Keith was killed and the captain of the Vimy mortally wounded. Later on the afternoon of 23 May the British finally decided to evacuate their troops from Boulogne. Three more destroyers (HMS Vimiera, HMS Venomous and HMS Venetia) were sent over to take part in the operation, with HMS Wild Swan following close behind.
They arrived at Boulogne at 6.30pm, just after a heavy German air raid that General Nehring claimed disabled three destroyers. The new ships were met by HMS Whitshed outside the harbour. Her commander, E. R. Conder, was now the senior naval officer present. He sent a message to Admiral Ramsey, the overall commander of the evacuations, reporting that he would not risk entering the port without air support. Fifty minutes later, at 7.20pm, with RAF fighters overhead the British flotilla began to enter the port.
Whitshed and Vimy went in first. They were each able to take on around 1,000 men, before withdrawing at 8.20pm. They were then followed in by the Wild Swan, Venomous and Venetia. HMS Venetia soon became the only British destroyer to be seriously damaged. Her captain was wounded and she was forced to back out of the port. All three ships became involved in a close range ship-to-shore battle, attacking German tanks with their quick firing naval guns, aiming over open sights at enemies only a few hundred yards away. The situation was made worse when the Germans captured the French coastal gun batteries largely intact, and turned them on the British ships. Despite this, at 9.30 the Wild Swan and the Venomous left port with 900 men on board between them.
By this point 2,900 men had been evacuated, but there were still 2,200 British soldiers in Boulogne. At 10.30pm an eighth destroyer, HMS Windsor reached the port, and was able to evacuate 600 men, amongst them many of the wounded and a naval demolition party that had first been sent in on 22 May. Finally, in the early hours of 24 May HMS Vimiera made the final trip into Boulogne. By now the fighting had died down for the night, and by 2.45 she had been able to take 1,300 men on board. A total of 4,360 men were rescued. Unfortunately a second destroyer, HMS Wessex, had failed to arrive, and so 300 men of the Welsh guard had to be left behind.
On the morning of 24 May the French garrison still held the old citadel, and was determined to fight on, protected by the 30 foot walls of the citadel. The Germans carried out a head-on attack. Using siege ladders, and supported by concentrated artillery fire, flame throwers and close range fire from anti-aircraft guns, by the end of the day the Germans had captured the citadel. On the next day (25 May) the remaining garrison finally surrendered. The Germans captured two generals and 5,000 Allied troops, most of them French. While not as famous as the defence of Calais, which was being conducted at almost the same time, the three day defence of Boulogne played a part in delayed the German advance towards Dunkirk, and gave the British and French time to consolidate their defensive positions west of Dunkirk.