America tacitly approved Germany's rearmament in 1935.It carried out the policy because of its resentment against Versailles Treaty and the development of European disarmament after the Great War.
Although Britain was rearming rapidly, the rearmament programme would not be complete until 1941, and in the meantime, Chamberlain continued in his efforts to preserve peace through diplomacy.
The French were not prepared to fight an offensive war, bombing Germany would merely invite retaliatory attacks which would undermine British rearmament, and intervention of any sort would antagonise the Soviet Union.