Which of the following factors contributed to the failure of Hitler's first attempt at Anschluss in 1934?

The failure of Hitler's first attempt at Anschluss in 1934 can primarily be attributed to Italy's opposition, specifically Mussolini's actions. During this period, Mussolini, who was the leader of Italy, was staunchly opposed to the idea of a unified Germany and Austria under Hitler's regime. He had concerns that such a move could embolden Hitler's ambitions further, potentially threatening Italy's own interests.

Mussolini had fortified his stance by mobilizing Italian troops to the Austrian border in response to the prospect of Anschluss. This military readiness sent a clear signal to Hitler that Italy would not tolerate the annexation of Austria, thereby significantly deterring any immediate actions that could lead to a successful takeover.

While support from Britain and France, internal opposition within Austria, and Germany's military restrictions were indeed factors to consider in the broader context of Hitler's expansionist aspirations, Mussolini's outright opposition at that time was a crucial element that directly impacted the failure of the Anschluss in 1934. Thus, understanding Mussolini's strategic positioning and the balance of power in Europe at that moment underscores why external factors played a significant role in thwarting Hitler's ambitions.