was supported by the continued practice of patrols of all four sectors by soldiers of all four occupying powers. Thus, occasionally Western Allied soldiers were on patrol in East Berlin as were Soviet soldiers in West Berlin. After the Wall was built, East Germany wanted to control Western Allied patrols upon entering or leaving East Berlin, a practice that the Western Allies regarded as unacceptable. After protests to the Soviets, the patrols continued uncontrolled on both sides, with the tacit agreement that the western Allies would not use their patrolling privileges for helping Easterners to flee to the West. In many ways, West Berlin functioned as the de facto 11th state of West Germany and was depicted on maps published in the West as being a part of West Germany. There was freedom of movement (to the extent allowed by geography) between West Berlin and West Germany. There were no separate immigration regulations for West Berlin, all immigration rules for West Germany being followed in West Berlin. West German entry visas issued to visitors were stamped with "for the Federal Republic of Germany, including the State of Berlin", in German "für die Bundesrepublik Deutschland einschl. [einschließlich] des Landes Berlin", prompting complaints from the Soviet Union. However, this wording remained on the visas throughout the rest of the entire period of West Berlin's existence. West Berlin remained under military occupation until 3 October 1990, the day of unification of East Germany, East and West Berlin with Federal Republic of Germany. The West German Federal Government, as well as the governments of most western nations, considered East Berlin to be a "separate entity" from East Germany, and while the Western Allies later opened embassies in East Berlin, they recognised the city only as the seat of government of the GDR, not as its capital. Communist countries, however, did not recognise West Berlin as part of West Germany and usually described it as a "third" German jurisdiction, called in German selbständige politische Einheit ("independent political unit"). On maps of East Berlin, West Berlin often did not appear as an adjacent urban area but as a monochrome terra incognita, sometimes showing the letters WB, meaning West Berlin, or overlaid with a legend or pictures. It was often labelled "Besonderes politisches Gebiet Westberlin" (West Berlin special political area). Immigration The Federal Republic of Germany issued West German passports to West Berliners on request that showed