How and why did Iran attack US bases: A timeline of escalating tensions

Tensions between Iran and the United States have been steadily escalating for months. After a US strike killed a top Iranian commander last week and Iran launched retaliation strikes on Wednesday.

April 8, 2019:  Washington declares Iran's elite Revolutionary Guard Corps a "terrorist" group. Its Quds Force, which operates abroad, is also put on the blacklist.

May 5:  White House national security adviser John Bolton announces the deployment of an aircraft carrier and a bomber task force to the Middle East.

May 8: A year after Washington unilaterally withdrew from an international 2015 deal curbing Iran's nuclear programme and reimposed sanctions, Tehran warns