The very first article of the Austrian constitution, adopted with the unification of 1955, states that the state shall never join a military union or allow foreign troops on it's soil.

In the «Stalin Note» of 1952 the Soviet Union proposed to unify Germany under the same condition of neutrality and similar proposals would continue until 1954, when Western Germany finally joined the NATO.

Interesting question. How can I mark this up to be informed about answers?

EDIT: Nevermind. I just found the subscribe button.