What was the main reason for the annexation of Austria by Germany?

The primary reason for the annexation of Austria by Germany, often referred to as the "Anschluss," was to expand German territory. This strategic move was part of Adolf Hitler's broader vision of uniting all ethnic Germans under one Reich, as Austria had a significant population of ethnic Germans. The annexation in 1938 was not only aimed at territorial expansion but also at consolidating power and influence in Central Europe, which aligned with the Nazi regime's nationalist and expansionist ideologies.

The other options, while they may have some relevance, do not capture the core motivation behind the annexation as effectively. The desire to form an alliance with Italy was secondary to the goal of territorial expansion. Securing borders was more of a post-facto justification rather than a main motive, and while economic resources may have been a consideration, the unification of German-speaking peoples was the driving force behind this action. The annexation was celebrated in Germany and among many in Austria at the time, reflecting the strong nationalist sentiment that characterized this period.