1812 — Great Britain

The War of 1812 hinged on international trade disputes and U.S. expansion.

1846 — Mexico

Following the Mexican-American War over territory, the U.S. annexed eight western states.

1898 — Spain

The U.S. entered into the Spanish struggle with Cuba over independence.

1917 — Germany

After remaining neutral for several years, the U.S. joined World War I.

1917 — Austria-Hungary

Involvement in WWI quickly deepened when the U.S. went to war with Germany’s ally.

1941 — Japan

A spectacular air attack on Pearl Harbor spurred the U.S. to enter World War II.

1941 — Germany

The U.S. responded in kind after Germany declared war first.

1942 — Bulgaria,

Hungary, Romania

The three German allies first declared war against the U.S.

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In many cases, presidents have asked Congress to pass legislation allowing or supporting the use of military force:

1798 — France

The fledgling U.S. Navy was ordered to protect American trading ships from the French.

1802 — Tripoli

The Navy was again ordered to protect commerce ships from what is today Libya.

1815 — Algeria

Congress denied a presidential request for war but allowed Navy action to protect trade from this other North Africa country.

1819-23 — Caribbean, Latin America

Rampant pirating prompted a military response to protect U.S. merchant ships.

1955 — Formosa

The U.S. acted to fend off communist China from seizing the island now known as Taiwan.

1957 — Middle East

In the midst of the Cold War, Congress authorized military force if any countries in the region were attacked by communist forces.

1964 — Southeast Asia

Following the Gulf of Tonkin incident, combat forces were sent to Vietnam and elsewhere in the region.

1983 — Lebanon

U.S. Marines were sent to this Mid-East country bordering Syria to quell violence and provide stability.

1991 — Iraq

The U.S. pushed Iraqi forces out of Kuwait following an invasion and occupation.

2001 — Global

A global fight against the al-Qaida terrorist network and any countries helping them followed deadly attacks in New York, Washington and Pennsylvania.

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Presidents have exerted executive power and used United Nations resolutions to wage military campaigns without first getting approval from Congress:

1950 — Korea

The U.S. sent air power and troops to the peninsula to repel invading communist North Korea forces backed by the Soviet Union.

1994 — Bosnia

The Clinton administration joined a NATO airstrike campaign to quell ethnic and religious fighting following a government disintegration.

Source: Congressional Research Service; American Journal of International Law

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