Prior to attack on biggest US military base in Middle East, US had already started taking ‘force protection’ measures.

Iran has responded to the United States’ direct involvement in the Iran-Israel conflict by targeting its military assets in the Middle East.

On Monday, Ali Akbar Velayati, an adviser to Supreme Leader Ayatollah Ali Khamenei, announced that bases used by US forces “in the region or elsewhere” could be attacked in retaliation for US attacks on Iran’s underground nuclear sites the previous day.

Later that evening, explosions were heard over Qatar’s capital, Doha, as Iran attacked Al Udeid Air Base, the largest US military base in the Middle East.

Here’s everything you need to know about Al Udeid: