However, the Berlin Wall was built and a barbed wire fence with minefields extended the entire north–south length of a divided Germany. The wall effectively isolated East Germany for the next twenty-eight years. But the American, British, and French Zones still remained in Berlin and access to the city was not challenged again. TACK HAMMER and STAIR STEP forces had served their purpose; their rapid deployment to France had unequivocally demonstrated the United States' determination to defend Berlin.