American jets hit targets in Syria on Tuesday in the US-led fight against Islamic State. Although the US has not declared war since 1942, this is the seventh country that Barack Obama, the holder of the Nobel Peace Prize, has bombed in as many years.

Syria has become the latest country to have been openly targeted by the US, with Washington predictably not seeking the approval of Syrian President Bashar Assad.

The US and NATO started a bombing campaign in the north of the country on Tuesday against Islamic State militants, who have taken over parts of the north and east of the country. The death toll from Tuesday’s campaign was put at 120, though this figure could rise, according to the Syrian Observatory for Human Rights, who also said that eight civilians had lost their lives.

When the Pentagon says that the conflict in Syria may take years to resolve, it is no joke – just take a look at the number of Washington’s “military engagements” during Obama’s administration.

Afghanistan (2001-present day)

It was only a matter of time following the September 11, 2001, terrorist attacks on US soil that Afghanistan would become the first country America would bomb in the 21st century, after the Taliban refused to hand over Al-Qaeda leader Osama Bin Laden.

Starting with the country’s largest cities – Kabul, Kandahar and Jalalabad, the US and its allies have become involved in a protracted conflict, which has seen tens of thousands of casualties inflicted. Although there has been a large-scale troop withdrawal, which started in June 2011 and will finish by the end of 2014, as the US looks to pass the baton of policing and providing security in Afghanistan to local forces. Yet airstrikes are still taking place.

The US has spent more than $100 billion on aid in Afghanistan since 2001 to train and equip the country's security forces and upgrade its infrastructure, while 2,200 American troops have been killed in Afghanistan since 2001, while around 20,000 have been wounded, according to AP.

US bombing campaigns have been a contentious issue with Afghanistan’s leadership, which has said that too many civilians have died as a result of American bombing missions. Just last week, American missiles killed 11 civilians in the east of the country.

"If America and Pakistan really want it, peace will come to Afghanistan," the country’s outgoing president, Hamid Karzai, said on September 23 as he was stepping down. "War in Afghanistan is based on the aims of foreigners. The war in Afghanistan is to the benefit of foreigners. But Afghans on both sides are the sacrificial lambs and victims of this war."

Yemen (2002-present day)

The death of 17 US navy personnel in October 2000, who were killed when the USS Cole was attacked in the port of Aden, Yemen, by Al-Qaeda, already put the country firmly on Washington’s radar. In November 2002, America needed no extra incentive to carry out its first bombing raid on Yemeni soil, with the country’s government giving the US the green light.

The target was Qaed Salim Sinan al-Harethi, who Washington believed was al-Qaeda’s chief operative in Yemen and was also a suspect in the bombing of the USS Cole. He was killed when a hellfire missile, guided from a pilotless aircraft hit the car he was traveling in. The US Deputy Defense Secretary at the time, Paul Wolfowitz, stated that it had been “a very successful tactical operation” and that such strikes were useful not only in killing terrorists, but in forcing Al-Qaeda to change its tactics.

While there were sporadic bombing campaigns carried out by the US, under President George W. Bush’s administration, there has been a significant escalation since Barack Obama came to power. US cables published by WikiLeaks showed that the Yemeni government has allowed US airstrikes to continue against suspected Al-Qaeda militants in the country.

US bombing raids in Yemen are almost solely carried out by drones and they have been increasing in intensity in recent years. However rights groups are becoming concerned that far too many civilian casualties are occurring as a result of America’s so-called “War on Terror.” A report by Human Rights Watch in 2013 analyzed six airstrikes in Yemen carried out since 2009. The organization found that out of the 82 people who died in the airstrikes, 57 were civilians.

Iraq (2003-2011)

The date is February 5, 2003 – the location, the United Nations in New York. The US Secretary of State, Colin Powell, has just delivered a speech to the UN, saying that Iraq has weapons of mass destruction – a pretext for Washington to get involved in yet another military conflict, as if having thousands of troops tied down in Afghanistan was not enough.

The first airstrikes on Iraq would take place on March 20, 2003, and within three weeks the Iraqi government had been toppled. However, just as in Afghanistan, gaining overall control of the country would not prove to be as easy, as the US and its allies came up against fierce resistance – at first from supporters of ousted President Saddam Hussein, later from various Sunni and Shiite resistance groups, and still later Al-Qaeda and its supporters.

The conflict and the US bombing campaigns proved to be disastrous for the Iraqi civilian population. An article published by AFP in October 2013, citing a study in the US, put the death toll at around half a million. Researchers stated that around 70 percent of Iraq deaths from 2003-11 were violent in nature, with most caused by gunshots, with the next most common cause of death car bombs and other explosions.

It also added that coalition forces were responsible for 35 percent of these violent deaths, or approximately 125,000 deaths.

Pakistan (2004-present day)

While drone attacks in Pakistan may have started under George W. Bush, the Obama administration has increased their frequency to unprecedented levels. According to The Bureau of Investigative Journalism, a website, there have been 390 drone strikes in Pakistan since 2004, of which a staggering 339 have been conducted since Obama came to power. This has led to almost 4,000 deaths, of which around one-quarter have been civilians.

Not surprisingly, the US-led drone strikes have led to plenty of friction with the Pakistani government.

“The use of drones is not only a violation of our territorial integrity but they are also detrimental to our efforts to eliminate terrorism from our country,” Pakistani Prime Minister Nawaz Sharif said in a meeting with Obama in October 2013, adding that the issue has become a “major irritant” in Pakistani-US relations.

Demonstrations against the use of drones by the US have been common in Pakistan. In December 2013, around 5,000 demonstrators called on the US to immediately stop the drone assaults on the country, which was organized by the Defense of Pakistan Council, which is comprised of 40 religious and political groups, AFP reported. Protesters chanted slogans and tried to block NATO supplies being transported to Afghanistan through Pakistan.

Meanwhile, a month earlier, the Pakistan Tehreek-e-Insaaf (PTI), led by the country’s cricket star Imran Khan, dropped the name of the Central Intelligence Agency (CIA) operative to police in a letter in which the party demanded that the agent face up to the “gross offence” of the drone strike.

The letter was released to the media. However, the name could not be independently verified.

“I would like to nominate the US clandestine agency CIA (Central Intelligence Agency) Station Chief in Islamabad ... and CIA Director John O. Brennan for committing the gross offences of committing murder and waging war against Pakistan,” PTI information secretary Shireen Mazarisaid wrote in the letter.

“CIA station chief is not a diplomatic post, therefore he does not enjoy any diplomatic immunity and is within the bounds of domestic laws of Pakistan,” the letter added. The complaint was lodged with Tal police station in Hangu district, northwestern Pakistan.

Somalia (2007-present day)

In January 2007, the US launched airstrikes against suspected Al-Qaeda leaders in Somalia, who Washington believed were guilty of bombing attacks on US Embassies in Kenya and Tanzania that killed more than 200 people. The US airstrikes had the full backing of the Somali President Abdullahi Yusuf Ahmed.

US involvement in Somalia has largely slipped under the radar, with significantly less international attention given to Washington’s “War on Terror” in the horn of Africa.

However, in early September, Somali jihadists in the group Al-Shabaab, which has links to Al-Qaeda, confirmed that their leader Ahmed Godane had been killed by US airstrikes, before warning of revenge attacks. US forces struck Godane's encampment in south-central Somalia with Hellfire missiles and laser-guided munitions, Reuters reported. This drone attack was the first in Somalia for seven months.

What of Libya?

Libya is perhaps the exception to the rule where European and NATO forces carried out most of the bombing campaigns. However, it was the US who was instrumental in drumming up support to try and topple former Libyan leader Muammar Gaddafi in March 2011. Barack Obama had given Gaddafi an ultimatum which alluded to: ‘Step down, or we will bomb you.’ When he refused to listen to Washington’s demands, military action was soon forthcoming.

The civil war was over within eight months, though chaos and fighting between rival factions in the country still continues while thousands of Libyans died on both sides during the original conflict, many of them civilians.