President or Congress? Who in the US has the power to declare war?

US presidents have long bypassed Congress’s authority, and dissenting lawmakers have often tried to fight back.

As United States President Donald Trump faces mounting global criticism for starting the war on Iran with Israel, he is also facing a battle at home with opposition lawmakers who have challenged his authority to conduct the conflict.

Democrats argue that Trump, a Republican, wrongly sidelined Congress to start the war on Iran and has failed to explain the reasons for it – or what the US’s endgame is. Trump’s cabinet says he has the right to order emergency measures in “self-defence” against an “imminent threat” posed by Iran.

On February 28, the day the US and Israel launched their strikes on Iran, Trump described the actions as “major combat operations”, not a war. Indeed, the two allies code-named the strikes, in which Iranian Supreme Leader Ali Khamenei and several other senior officials were killed in Tehran, Operation Epic Fury.

In early March, Republican senators and one Democrat rejected a Democratic-led war powers resolution by a vote of 53-47. It sought to halt further US action in Iran and essentially end the war. Supporters of the resolution argued that Trump had exceeded his constitutional authority by launching the war. Under Article II of the US Constitution, presidents are permitted to launch such attacks only in self-defence – in response to an immediate threat. Otherwise, Congress has the sole power to declare war.

Trump has justified the attacks by arguing that despite holding talks with Iran, he believed Tehran was planning to strike first – thus invoking the “self-defence” justification.