Timeline of Islamic State group's surge in Iraq leading up to the battle over Mosul Dam

BAGHDAD – A timeline of key events in Iraq as the Islamic State extremist group, formerly known as the Islamic State of Iraq and the Levant, started to grab land in the Sunni heartland of western and northern Iraq.

April 30 — Iraq holds its third national elections since the U.S.-led invasion that toppled Saddam Hussein. The parliamentary elections are also the first such poll since the 2011 U.S. army withdrawal. No balloting was held in parts of Sunni-dominated Anbar province where security forces were fighting militants.

June 6 — A suicide bomber targets a group of pro-government, anti-militant Sunni militiamen, killing eight people including the prominent local leader Mohammed Khamis Abu Risha, the nephew of the influential tribal leader Ahmed Abu Risha. His brother had led the formation of the Sahwa — an anti-al-Qaida militia allied with U.S. forces — until his assassination in 2007. The Sahwa, also known as the Sons of Iraq, later disbanded.

June 10 — The al-Qaida breakaway group, the Islamic State of Iraq and the Levant, takes over Iraq's second-largest city of Mosul, followed by Saddam Hussein's hometown of Tikrit and smaller communities in the Sunni heartland as government forces melt away.

June 23 — Iraq-based powerful Shiite spiritual leader, Grand Ayatollah Ali al-Sistani, calls on Iraqis to join the security forces to fight Sunni extremist fighters.

June 29 — The group declares the establishment of an Islamic state, or caliphate, in territories it controls in Iraq and Syria and demands allegiance from Muslims worldwide. It declares the group's chief, Abu Bakr al-Baghdadi, as the leader of the new caliphate. The group renames itself the Islamic State.

July 1 — The United Nations announces June the deadliest month in Iraq since at least April 2005 with more than 2,400 Iraqis killed.

July 5 — A man purporting to be Abu Bakr al-Baghdadi makes his first public appearance, delivering a sermon at a mosque in Mosul.

Aug. 7 — The Islamic State militant seize the strategic Mosul Dam, pushing Kurdish peshmerga forces from a number of towns and forcing hundreds of thousands of minority Yazidis to flee.

Aug. 8 — The U.S. begins targeting fighters from the Islamic State with airstrikes.

Aug. 18 — Boosted by U.S. airstrikes, Iraqi and Kurdish forces say they wrest back control of the Mosul Dam as fighting was reported to be underway for the rest of the strategic complex. The Islamic State group denied the claim, insisting it was still in control of the facility.