Although the American public has never drawn sharp distinctions between alliances, coalitions, and ententes, its leaders have frequently acted in a way that indicated that they understood the differences. Alliances are properly formal agreements between nations that call for specific joint action and responses to given political situations. They can be outlined verbally, but they are normally committed to paper and are, therefore, recognized in international law. Although alliances relate to wartime situations, they are usually concluded in times of peace and last for significant periods of time.
Coalitions bring to mind the various European joint efforts against France in the late eighteenth and early nineteenth centuries. Those wars saw various nations unite in military action against France frequently only after the fighting had actually begun. Short term and often not defined by written agreements, coalitions aim simply at the military defeat of a common enemy and do not relate to postwar considerations. Although the term is rarely applied, Russo-American cooperation during World War II against Nazi Germany was a coalition rather than an alliance. The only common ground was military victory over the enemy, and attempts by both nations to expand that limited relationship met with failure.
Entente, properly used, describes a far deeper relationship between nations than either alliance or coalition. An entente becomes possible only when two or more nations share a set of political goals and perceptions. The most obvious entente in American history has been the one that began to develop between Great Britain and the United States after the War of 1812. Frequently subjected to great strains, that entente was formalized as an alliance during World War II and the Cold War era. Such an entente is more a friendship than an alliance or coalition stimulated by sheer power politics, although the realities of international relations are never completely ignored.