Baltic Sea near Memel after over-running the headquarters of the 3rd Panzer Army. As a result, Army Group North was cut off from East Prussia. Hitler's military advisors—notably Heinz Guderian, the Chief of the German General Staff—urged evacuation and utilisation of the troops to stabilise the front in central Europe. However, Hitler refused, and ordered the German forces in Courland and the Estonian islands Hiiumaa (Dagö) and Saaremaa (Ösel) to hold out, believing them necessary to protect German submarine bases along the Baltic coast. Hitler still believed the war could be won, and hoped that Dönitz's new Type XXI U-boat technology could bring victory to Germany in the Battle of the Atlantic, forcing the Allies out of Western Europe. This would allow German forces to focus on the Eastern Front, using the Courland Pocket as a springboard for a new offensive. Hitler's refusal to evacuate the Army Group resulted in the entrenchment of more than 200,000 German troops largely of the 16th Army and 18th Army, in what was to become known to the Germans as the "Courland Bridgehead". Thirty-three divisions of the Army Group North, commanded by Field-Marshall Ferdinand Schörner, were cut off from East Prussia and spread out along a front reaching from Riga to Liepāja, retreating to the more defensible Courland position, abandoning Riga. Soviet forces launched six major offensives against the German and Latvian forces entrenched in the Courland Pocket between 15 October 1944 and 4 April 1945. The German two-phase withdrawals during the execution of the second stage of the Soviet Baltic Offensive (14 September – 24 November 1944), subsequent to the pocket being formed in the Baltic Offensive's first stage, the Memel Offensive Operation. Timeline From 15 to 22 October 1944 – Soviets launched the Riga Offensive Operation on the 15th at 10:00 after conducting a heavy artillery barrage. Hitler permitted the Army Group Commander, Ferdinand Schoerner, to commence withdrawal from Riga on 11 October, and the city was taken by the 3rd Baltic Front on 13 October. The front stabilised with the main remnant of Army Group North isolated in the peninsula. From 27 October to 25 November – Soviets launched an offensive trying to break through the front toward Skrunda and Saldus including at one point initiating a simultaneous attack by 52 divisions. Soviet forces also attacked southeast of Liepāja in an attempt to capture that port. 80 divisions assaulted the Germans