President Barack Obama has presided over billions spent battling the Islamic State, despite, by his own admission, lacking a clear and complete strategy to defeat the terror group.

War against Islamic State has cost a total of $2.91 billion, averaging $9.2 million per day, according to the Pentagon. More than 50 percent of the cost is directly tied to airstrikes, The Hill reports.

Republican Sen. John McCain has criticized the campaign against Islamic State as too weak, noting that 75 percent of airstrike missions return without firing a weapon. Speaking on CBS’s “Face The Nation” in late May, McCain said, “We need more troops on the ground. We need forward air controllers. But just referring to airstrikes, do you know that 75 percent of those combat missions return to base without having fired a weapon? It’s because we don’t have somebody on the ground who can identify … a moving target. … We found in Vietnam that if you don’t have the right strategy, airpower is minimal in its effect.”

In Syria, a $500 million program to train and equip rebels against Islamic State is stagnant. Secretary of Defense Ash Carter admitted the program has only produced 60 Syrian trainees, attributing it to a strict vetting process. Originally, U.S. officials hoped to ready 5,400 rebels per year, The Associated Press reports.

Just what do these numbers mean to the average American? Well…

In early June, Obama said the U.S. still didn’t have a complete strategy to defeat Islamic State, adding he is waiting for the Pentagon to provide one.

Islamic State declared the establishment of its “caliphate” last year, capturing territory from Iraq to Syria until the U.S. began taking an active role in the conflict after militants trapped thousands of Yezidi civilians on Mt. Sinjar last year.

The terror group publicly executed U.S. journalists James Foley and Steven Sotloff, as well as former U.S. Army Ranger Peter Kassig. Aid worker Kayla Mueller was also captured by Islamic State and later killed. (RELATED: ISIS Beheads Another British Hostage, Threatens Former US Army Ranger)

Some former U.S. veterans or volunteers with no military experience have joined ranks with Kurdish forces battling Islamic State in Iraq and Syria. Keith Broomfield died while fighting with the Kurdish YPG militia in early June. (RELATED: US Man Who Died Fighting ISIS Was Guided By God, Says Father)

Islamic State threatened U.S. military personnel in March, releasing a list of names, photos and home addresses online and encouraged state-side sympathizers to kill them.

The U.S. airstrike campaign has failed to curb Islamic State expansion and is often criticized as too weak, averaging 12 strikes per day. During the first 30 days of the invasion of Iraq, the U.S. launched an average of 691, according to The Washington Post.

The air campaign became particularly controverisal after the U.S. provided cover for Iran-backed, Shiite militias fighting Islamic State, some of whom targeted U.S. forces during the war in Iraq. The Iranian proxies have also perpetrated acts of sectarian violence. (RELATED: Rampage In Iraqi Village Shows Cracks In US Middle East Policy)

U.S. airstrikes helped free the Syria-Turkey border city of Kobani from Islamic State in January. But jihadis infiltrated Kobani in late June and committed a bloody massacre of Syrian civilians prior to Kurdish forces regaining control.

Sources: Meals for a four-person family, income taxes, in-state tuition, 2015 Ford F-150s, college debt, pallets of Pabst Blue Ribbon, Philadelphia’s population, Wyoming’s college graduates, Arizona State University’s undergraduate enrollment and Madison Square Garden’s capacity.

Jacob Bojesson contributed to this article.

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Content created by The Daily Caller News Foundation is available without charge to any eligible news publisher that can provide a large audience. For licensing opportunities of our original content, please contact licensing@dailycallernewsfoundation.org.