Questions: Which tactic did the Americans conduct first upon their entry into the war? - Assassinate Hitler - Focus on Europe first - Construction of the atomic bomb - Focus on Japan first

The answer is B: Focus on Europe first.

Explanation for each option:

A. Assassinate Hitler - This was not a tactic that the Americans conducted upon their entry into the war. While there were various plots to assassinate Hitler, they were not a primary focus of American military strategy.

B. Focus on Europe first - This is the correct answer. The United States, along with its Allies, adopted a "Europe First" strategy, prioritizing the defeat of Nazi Germany before turning full attention to Japan. This decision was made because Germany was considered the more significant threat to the Allies at the time.

C. Construction of the atomic bomb - While the United States did work on the Manhattan Project to develop the atomic bomb during World War II, this was not the first tactic upon entering the war. The project was a long-term effort that culminated later in the war.

D. Focus on Japan first - This is incorrect. Although the U.S. did engage in the Pacific Theater against Japan, the strategic decision was to focus on Europe first, as mentioned above. The Pacific campaign was important but secondary to the European front initially.