Following these events the 1st Panzer Division continued to push forward, reaching the Channel coast near Calais on 23 May 1940, where they encountered heavy British resistance. The 10th Panzer Division was tasked with taking Calais, while Guderian ordered the 1st Panzer Division to head for Gravelines. Elements of the "Panzer-Brigade" I, the subordinated "Infanterie-Regiment" (motorized) "Großdeutschland" and the "Panzeraufklärungsabteilung" 4 (Tank Reconnaissance Detachment 4) reached the Aa river south of Gravelines that night, southwest of Dunkirk. Strachwitz again went on one of his solo runs, penetrated the French and British lines and almost reached Dunkirk, where he observed the evacuation of British and allied forces by sea. He quickly reported his observations to his divisional command. The Ia (operations officer) "Major im Generalstab" (in the General Staff) Walther Wenck informed him that aerial reconnaissance had made the same observations but the "Führerhauptquartier" had ordered the Panzers to halt. Three days later Hitler ordered the attack to continue but the opportunity to capture the majority of the Allied forces had been lost. The remaining defenders of Dunkirk continued to hold out until 4 June.