Question

in the 1930s, germany first began to expand aggressively by
invading russia.
rebuilding the german military.
joining german forces with italy.
making a pact with china.

Explanation:

In the 1930s, Germany first started its aggressive expansion by rebuilding its military in violation of the Treaty of Versailles. This was a key step in its path towards more aggressive actions later. Invading Russia happened in 1941, joining forces with Italy was not the first - step of aggression, and there was no significant aggressive - related pact with China in the 1930s as part of Germany's initial aggressive moves.

Answer:

rebuilding the German military