President Barack Obama authorised air strikes in Iraq to help take control of the Mosul Dam, the White House has said.
The President believes failure to secure the dam would threaten civilians and the US embassy in Baghdad, it said.
"The failure of the Mosul Dam could threaten the lives of large numbers of civilians, threaten US personnel and facilities - including the US embassy in Baghdad - and prevent the Iraqi government from providing critical services to the Iraqi populace," the White House said in a statement.
"These operations are limited in their nature, duration, and scope and are being undertaken in coordination with and at the request of the government of Iraq."
Kurdish Peshmerga fighters have emerged victorious in the battle for Mosul Dam, but the question is - what will their next move be?
An ITV News team at Mosul Dam was with victorious Kurdish Peshmerga fighters at the complex earlier today.
ITV News joined a Kurdish unit fighting Islamist militants near Irbil and found them using tanks from the 1950s and short on ammunition.