By 1940 the Third Reich had occupied many of the Alpine countries. Austria underwent a political coup that made it part of the Third Reich; France had been invaded and Italy was a fascist regime. Switzerland was the only country to luckily avoid invasion. The Swiss Confederate mobilized its troops—the country follows the doctrine of "armed neutrality" with all males required to have military training—a number that General Eisenhower estimated to be about 850,000. The Swiss commanders wired the infrastructure leading into the country, and threatening to destroy bridges, railway tunnels and passes in the event of a Nazi invasion, and then they retreated to the heart of the mountain peaks where conditions were harsher and a military invasion would involve difficult and protracted battles.