The United States and Israel continued airstrikes on Iran on Monday, while Tehran retaliated against U.S. bases and Israeli targets in the Middle East, with violence spreading across the region.

How long will the conflict between the U.S. and Iran last? President Trump shared a timeline on Monday. (AP Photo) ...

Amid ongoing strikes against Lebanon, the Israel Defense Forces said, "The strikes continue - their intensity will increase." ...

Amid ongoing strikes against Lebanon, the Israel Defense Forces said, "The strikes continue - their intensity will increase." ...

With no sign of the conflict abating anytime soon, President Trump said operations are likely to last four to five weeks but that he was prepared “to go far longer than that.” ...

The State Department urged U.S. citizens to leave more than a dozen Middle Eastern countries due to safety risks.

Follow NBC News' live coverage as the U.S. and Israel attack Iran, Tehran hits back across the Gulf, and Hezbollah strikes from Lebanon, while Iran chooses a new supreme leader after the killing of ...

How long will the conflict between the U.S. and Iran last? President Trump shared a timeline on Monday. (AP Photo) ...

The U.S. military said Monday that the number of Americans killed during the ongoing conflict with Iran now stands at six.

Trump said the strikes were intended to eliminate "imminent threats" from Iran and prevent the country from obtaining a ...

President Donald Trump vowed to avenge fallen US servicemembers amid the war with Iran as Israel expanded the conflict with more strikes in Tehran and against Hezbollah in Lebanon on Monday.

The U.S. and Israeli air war against Iran widened on Monday, with no end in sight as Israel attacked Lebanon in response to ...