Third Army's intelligence section had already determined that the Germans intended to make the most of the ring of forts around Metz, the ancient gateway city through which so many invading armies had passed. Metz was to be the linchpin in the Germans' defensive strategy. An army had not directly taken the city since 1552. It had been captured after a 54-day siege during the Franco-Prussian War and had been fortified by the Germans in World War I. However, the string of fortresses were left in ruins.