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Bombing Iraq has become a recurring theme for U.S. presidents.

President Barack Obama on Thursday became the fourth consecutive commander-in-chief to conduct airstrikes in Iraq when U.S. military aircraft attacked militants of the Islamic State in Iraq and Syria (ISIS).

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Two F/A-18 aircraft dropped 500-pound laser-guided bombs on ISIS mobile artillery near Erbil, Pentagon press secretary Rear Adm. John Kirby said in a statement. The weapons were being used to shell Kurdish forces defending the city, where U.S. diplomats and military advisers are located.

Let's recap the history of U.S. bombing campaigns in Iraq.

President George H.W. Bush

Bush launched the Persian Gulf War in response to Iraqi dictator Saddam Hussein's invasion of Kuwait in August 1990.

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Diplomatic efforts and sanctions failed to deter Hussein, so the United States and other nations resorted to military force. Operation Desert Storm began on Jan. 17, 1991, when allied air forces bombed targets in Iraq and Kuwait.

"Why act now?" Bush asked in a televised address. "The answer is clear, the world could could wait no longer."

Bush added that allied forces "have no choice” but to drive Saddam from Kuwait by force. “We will not fail," he said.

The strikes targeted Iraq's nuclear facilities, chemical weapons arsenal, and artillery and tanks, Bush said.

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Coalition forces launched a ground campaign in February. The war succeeded in driving Iraqi forces out of Kuwait, but Hussein remained in power.

President Bill Clinton

Following the Gulf War, the United Nations imposed measures designed to strip Iraq of its chemical and biological weapons and halt its efforts to develop a nuclear bomb.

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Hussein's government had a poor record of cooperating with international weapons inspectors and called for sanctions to be lifted. Inspectors and western governments in turn accused Hussein of hiding weapons of mass destruction.

Tensions reached a boiling point in 1998 when U.N. inspectors left Iraq amid complaints about interference from Hussein's regime. The United States and United Kingdom began a bombing campaign on Dec. 16, 1998, known as Operation Desert Fox, against Iraqi weapons facilities.

"Saddam Hussein must not be allowed to threaten his neighbors or the world with nuclear arms, poison gas, or biological weapons," Clinton said during a televised speech from the Oval Office.

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Noting Iraq's previous use of chemical weapons against Iranian and Kurdish civilians, Clinton said, "I have no doubt today that left unchecked, Saddam Hussein will use these terrible weapons again."

The initial salvo involved more than 200 cruise missiles launched from warships in the Persian Gulf, according to The Washington Post. The campaign lasted four days.

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U.S. officials were confident at the time that the strikes had degraded Iraq's arsenal of weapons of mass destruction. But the issue would resurface almost five years later.

President George W. Bush

The U.S. continued to conduct limited airstrikes on Iraqi military facilities after Operation Desert Fox. At least eight attacks were carried out in 2001 during President George W. Bush's first year in office, according to The Associated Press.

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Hostilities escalated in March 2003 when Bush decided to go to war with Iraq. Bush and his British counterpart, Prime Minister Tony Blair, argued that Iraq was continuing to hide weapons of mass destruction from inspectors; they argued that Hussein needed to be disarmed through military force.

The decision was highly controversial. Critics dismissed U.S. intelligence on Iraq's weapons as flawed, argued that Bush used the 9/11 terrorist attacks as a pretext for war, and slammed the United States and Britain for attacking without U.N. approval.

Coalition forces began Operation Iraqi Freedom with a "shock and awe" campaign on March 19, 2003. The objective was to drive Hussein from power.

(Scroll to the 40:00 mark to witness the beginning of the attack).

"Our nation enters this conflict reluctantly, but its purpose is sure," Bush said in an Oval Office address. "The people of the United States and its friends and allies will not live at the mercy of an outlaw regime that threatens the peace with mass murder."

Less than a month later, allied forces toppled Hussein's regime. Bush declared an end to major combat operations on May 1, 2003, in a much-criticized speech standing under a banner that read "Mission Accomplished."

J. Scott Applewhite, File/AP Photo

U.S. forces then spent the next eight years fighting insurgent groups and trying to establish a stable Iraqi government.

President Barack Obama

Obama campaigned for president in 2008 vowing to end the war in Iraq, which cost the lives of 4,200 U.S. service members during its first six years.

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Obama began withdrawing troops early in his presidency. The last combat forces left the country in December 2011.

"We’re leaving behind a sovereign, stable and self-reliant Iraq, with a representative government that was elected by its people," Obama said during a speech that month in Fort Bragg, North Carolina.

But over the last several months, tensions between the Iraqi government and Sunni militant groups worsened. That contributed to the rise of ISIS, which has carried out violent attacks that have destabilized the country.

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The group captured Mosul, Iraq's largest Christian city, in June. Recently ISIS surrounded a group of 40,000 Yazidis, an ethnic-religious minority, and carried out attacks on the Kurdish city of Erbil. In response, the United States on Thursday launched airstrikes on ISIS artillery locations and air dropped humanitarian aid to the Yazidis.

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The strikes were targeted and ground troops would not return to Iraq, Obama said during a speech in the State Dining Room. He said the United States had a responsibility to act.

“We intend to stay vigilant, and take action if these terrorist forces threaten our personnel or facilities anywhere in Iraq,” Obama said.

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The planes involved in the latest airstrike were launched from the aircraft carrier USS George H.W. Bush.

Jordan Fabian is Fusion's politics editor, writing about campaigns, Congress, immigration, and more. When he's not working, you can find him at the ice rink or at home with his wife, Melissa.