A subsidiary operation was executed to capture German long-range, heavy artillery at Cap Gris Nez, which threatened the sea approaches to Boulogne.

The 7th and 8th Canadian Infantry Brigades started the main attack from south-west of Calais and cleared the outer defences on the southern and western sides of the port.

[3] After his surrender, the fortress commander, Oberstleutnant Ludwig Schroeder, called the garrison, consisting of 7,500 sailors, airmen and soldiers, of whom only 2,500 were fit for use as infantry, "mere rubbish".

[3] The French coast goes northwards from Boulogne and turns sharply at Cap Gris Nez to a line roughly south to north-east, which continues beyond the Belgian border.

[5] The Germans had broken the drainage systems, flooding the hinterland and added large barbed wire entanglements, minefields and blockhouses.

[4] The Allies judged it essential to silence the German heavy coastal batteries around Calais which could threaten Boulogne-bound shipping and bombard Dover and inland targets.

Infantry assaults would follow, preceded by local bombardments to keep the defenders under cover until too late to be effective and accompanied by Churchill Crocodile and Wasp flame-throwing vehicles to act as final "persuaders".

The eastern side of the city was screened by The Cameron Highlanders of Ottawa to prevent a break-out; the 9th Canadian Brigade would take over from the 7th Reconnaissance Regiment at Cape Gris Nez and prepare to capture the batteries there.

Montgomery had been directed to bring Antwerp into operation and ordered General Harry Crerar, commander of the First Canadian Army, quickly to capture the Channel Ports.

[4] The 7th and 8th Canadian Infantry Brigades opened their attack on Calais and its western coastal defences at 10:15 a.m., on 25 September after a day's delay, following preparatory air and artillery bombardments.

[8] The Régiment de la Chaudière were to advance through Escalles, taking Cap Blanc Nez and link up near Sangatte with the North Shore Regiment.

The North Shores had the difficult task of taking the fortified Noires Mottes, high ground near Sangatte and the site of Batterie Lindemann.

Negotiations were opened with the help of German prisoners and the Noires Mottes garrison surrendered at first light on the following morning, 26 September.

The 1st Canadian Scottish, the Regina Rifles and The Royal Montreal Regiment were to attack through the Belle Vue fortifications to the seafront just east of Sangatte.

The 8th Canadian Brigade reached Sangatte on the morning of 26 September, with its objectives complete, it was transferred to the eastern side, relieved the Camerons and applied pressure from another direction.

[16] The Canadians attacked immediately after the truce expired, despite German attempts to surrender; Crerar said that "the Hun, if they wished to quit, could march out with their hands up, without arms, and flying white flags in the normal manner".

Schroeder had ordered the garrison to cease resistance and the 7th Canadian Brigade, entering from the west, met no opposition, German troops surrendering everywhere.

[21] On 29 September, artillery opened fire at 6:35 a.m. and the infantry attack began after ten minutes behind a creeping barrage that kept the defenders under cover.

The concrete walls were impervious even to AVRE petard mortars but their noise and concussion, along with hand grenades thrown into embrasures, induced the German gunners to surrender by mid-morning.

[5] The reduction of the German heavy coastal batteries allowed use of Boulogne; mine-sweeping had commenced within hours of the success of the 9th Canadian Brigade.