Study smarter with Fiveable
Get study guides, practice questions, and cheatsheets for all your subjects. Join 500,000+ students with a 96% pass rate.
Wars have been the crucible in which American identity, territorial boundaries, and global power were forged. On the AP exam, you're being tested on more than dates and battles—you need to understand why conflicts erupted, how they transformed American society, and what lasting consequences they produced. These wars connect to major course themes: expansion and Manifest Destiny, debates over slavery and federal power, the rise of American imperialism, and Cold War containment policy.
Each war on this list illustrates broader patterns: the tension between ideals and interests, the expansion of executive power during wartime, and the social transformations that accompany military conflict. Don't just memorize which treaty ended which war—know what concept each conflict demonstrates. When an FRQ asks about territorial expansion, sectional crisis, or American foreign policy, these wars are your go-to evidence.
These early conflicts established American sovereignty and forged a sense of national identity. The key mechanism here is nation-building—wars that defined what America was and who belonged to it.
Compare: American Revolution vs. War of 1812—both involved conflict with Britain and boosted American nationalism, but the Revolution created the nation while the War of 1812 confirmed its survival. If an FRQ asks about the development of national identity, use both as bookends.
These conflicts fueled territorial growth under the banner of Manifest Destiny while intensifying debates over slavery's expansion. The underlying tension: every acre gained raised the question of whether it would be free or slave territory.
Compare: Mexican-American War vs. Civil War—the first created the territorial crisis over slavery's expansion; the second resolved it through force. The Mexican Cession made the Wilmot Proviso necessary; the Wilmot Proviso's failure made the Civil War inevitable. This cause-and-effect chain is prime FRQ material.
The late 19th century saw the U.S. project power beyond its continental borders. The driving mechanism was a combination of economic interests, strategic concerns, and ideological justifications about spreading "civilization."
Compare: Mexican-American War vs. Spanish-American War—both expanded U.S. territory through military victory, but the Mexican-American War added contiguous land while the Spanish-American War created an overseas empire. The first intensified the slavery debate; the second sparked debates about imperialism and citizenship.
America's involvement in two world wars transformed it from a regional power into a global superpower. These conflicts demonstrate the tension between isolationism and internationalism in American foreign policy.
Compare: WWI vs. WWII—both pulled America from isolationism into global conflict, but WWI ended with U.S. retreat from international commitments while WWII established permanent American global leadership. The Senate rejected the League of Nations; it embraced the United Nations. This shift from isolationism to internationalism is a key AP theme.
The ideological struggle between capitalism and communism shaped American foreign policy for nearly half a century. The containment doctrine—preventing the spread of communism without direct war with the Soviet Union—led to military interventions in Korea and Vietnam.
Compare: Korean War vs. Vietnam War—both were Cold War containment efforts in Asia, but Korea ended in stalemate while Vietnam ended in communist victory. Korea maintained bipartisan support; Vietnam sparked massive domestic opposition. Both raised questions about executive power, but Vietnam's Pentagon Papers and the War Powers Act (1973) represented a direct congressional pushback.
| Concept | Best Examples |
|---|---|
| Nation-building and sovereignty | American Revolution, War of 1812 |
| Manifest Destiny and territorial expansion | Mexican-American War, Spanish-American War |
| Slavery and sectional crisis | Mexican-American War, Civil War |
| Rise of American imperialism | Spanish-American War, WWI |
| Isolationism vs. internationalism | WWI, WWII |
| Cold War containment | Korean War, Vietnam War |
| Executive power in wartime | Civil War, Vietnam War, WWII |
| Domestic social transformation | WWI (Great Migration), WWII (women/minorities), Vietnam (anti-war movement) |
Which two wars most directly illustrate the tension between Manifest Destiny and the slavery debate? What specific events or documents connect them?
Compare the outcomes of WWI and WWII in terms of American international commitments. Why did the U.S. reject the League of Nations but embrace the United Nations?
How did the Korean War and Vietnam War both reflect containment policy, and what key differences explain their different levels of domestic support?
If an FRQ asked you to trace the development of American imperialism, which three wars would you use as evidence, and what would each demonstrate?
Compare the constitutional questions raised by the Gulf of Tonkin Resolution and the Emancipation Proclamation. How did each expand executive power during wartime, and what were the long-term consequences?