up with the airborne troops in LeMuy. French troops had been pouring ashore since 16August, passing to the left of the American troops with the objective of Toulon and Marseille. By the night of 16/17 August, Army Group G headquarters realized that it could not drive the Allies back into the sea. Simultaneously in northern France, the encirclement of the Falaise pocket threatened the loss of large numbers of German forces. Given the precarious situation, Adolf Hitler moved away from his "no step backwards" agenda and agreed to an OKW plan for the complete withdrawal of Army GroupsG and B. The OKW plan was for all German forces (except the stationary fortress troops) in southern France to move north to link up with Army GroupB to form a new defensive line from Sens through Dijon to the Swiss frontier. Two German divisions (the 148th and 157th) were to retreat into the French-Italian Alps. The Allies were privy to the German plan through Ultra interception. The German Navy's response was minimal. The Kriegsmarine had some 25 surface ships (mostly torpedo boats and smaller) though the main anti-invasion force, 10th Torpedo Boat Flotilla based at Genoa, had just four torpedo boats fit for service during Dragoon and this force took no action against the invasion fleet. There were two actions against the Allied naval forces taken by other units. On 15 August, off Port-Cros, the US destroyer encountered two German warships and in a short action sank both. On 17 August, off La Ciotat, a force of two German warships encountered a force of PT boats and gunboats staging a diversionary attack. Their destroyer escort engaged both vessels, and after an hour-long gun battle both German vessels were sunk. The Kriegsmarine also had a U-boat force based at Toulon operating in the Western Mediterranean; By the summer of 1944 this had been reduced to eight U-boats, and in air-raids prior to Dragoon five were destroyed. On the night of 17 August one boat attempted to sortie; she ran aground leaving harbour and was scuttled by her crew. The other two U-boats took no action, and were scuttled to avoid capture before the fall of Toulon. German withdrawal The Germans started the withdrawal, while the motorized Allied forces broke out from their beachheads and pursued the German units from behind. The rapid Allied advance posed a major threat for the Germans, who could