on the morning of 25 may, guderian found "leibstandarte" in defiance of the order to not cross the aa, as "leibstandarte" commander sepp dietrich had decided to cross it and take the wattenberg hill on the other side of the river at watten. this 72 metre elevation had been determined by dietrich to be a decisive strategic weakness to any german unit on the other side of the river. guderian agreed with dietrich's assessment, and, in defiance of the order, allowed "leibstandarte" and "großdeutschland" to maintain their advanced positions. parts of 2nd panzer divisions advanced towards the river's south bank to back up the northwards maneuvre. at the same time, 10th panzer division's ultimatum to the besieged allied units at calais was rejected by claude nicholson, the british commander of the allied forces. boulogne fell into the hands of 2nd panzer division as the last remainder of the allied forces surrendered, even though 4,286 allied soldiers were successfully evacuated by the royal navy. the directive "korpsbefehl nr. 13" was given out at 11:00 on may 25 and assigned defensive duties on the german right flank to 10th panzer division and the defense of the german left to 2nd panzer division, separated at audresselles. in the meantime, 1st panzer division would defend at st momelin.