The U.S. launched cruise missiles against Syria Friday, a day after President Trump said a chemical attack that killed dozens in a northern part of the country "crossed many, many lines."

The move has many Americans wondering if the U.S. is officially at war.

So how is war officially declared in the U.S.?

In short, only Congress has the power to formally declare war, according to the Constitution. 

The founders of the Constitution denied the President the authority to go to war without consenting with an open forum of the country's representatives, according to the United States House of  Representatives website. The idea was to avoid concentrating too much power in the hands of one or few.

For most of U.S. history, the Constitution's orders on war matters have been followed and the President has sought Congress to declare war.

However, the Constitution also names the President "Commander in Chief", giving war powers to both legislative and the executive branch.

In modern times, especially after World War II, the President has taken warfare action without a formal declaration of war from Congress. Instead, there have been congressional authorizations of use of military force (AUMF).

When Congress started first started granting AUMFs, actions were much more limited than formal war but over time, presidents have been granted more leisure in power. 

The U.S. has engaged in conflicts through AUMFS in places such as Vietnam and Iraq, but the nation has not formally declared war through Congress since 1942.

Congress has officially declared war 11 times in the country's history.

The last formal war was against Rumania in June of 1942 during World War II. The first formal declaration of war was the War of 1812 against Great Britain.

In 1973, the War Powers Resolution, which is sometimes referred to as the War Powers Act, was passed by Congress in the aftermath of the Vietnam War to provide a set of rules both the President and Congress must follow in situations where the U.S. plans to use force abroad. The idea behind the federal law is to check the President's power when faced with conflict and make sure joint decisions are made.