The Islamic State of Iraq and the Levant (ISIS) rakes in over $1 million a day and commands"a volume of resources and territory unmatched in the history of extremist organizations," according to Janine Davidson and Emerson Brookings of the Council on Foreign Relations.
The Al Qaeda splinter group has massacred members of Iraq's Yazidi religious minority and broadcast the murder of an American journalist on YouTube.
Now the target of a sustained campaign of American airstrikes, ISIS has previously declared the establishment of a caliphate and changed its name to simply the Islamic State, underscoring its ambition to become a permanent feature on the map of the Middle East.
ISIS wouldn't have been able to carve out such a vast domain, or present itself as a state-like entity capable of controlling territory and ruling over a population of millions, if it hadn't been armed to the hilt, partly from its seizure of military equipment from fleeing Iraqi soldiers and plundered Syrian military bases.
When ISIS overran Mosul, Iraq's second-largest city, in June, it captured weaponry that allowed the group to arm itself like a conventional army, rather than a ragtag insurgency.
"You lost approximately three divisions worth of equipment and probably at least three depots in that area," Anthony Cordesman, a security analyst at the Washington-based Center for Strategic and International Studies, told The Wall Street Journal.
More recently, ISIS captured anti-aircraft weaponry from an air force base in eastern Syria, including rockets capable of bringing down planes flying at 16,000 feet.
A large quantity of the weapons that ISIS has seized were supplied by the U.S. to the Iraqi Army. ISIS also fields weapons produced in Russia, China, the Balkans, and Iran.
T-55 Tanks
The T-55 tank series is a Soviet tank line that was produced from the end of World War II through the 1980s. It is estimated that ISIS has about 30 of these tanks, although it is unknown how well the organization can maintain and operate them.
Despite the tanks' age, they remain operational in up to 50 armies around the world. The tanks feature heavy armor, along with a 100-mm rifled gun and a secondary 7.62-mm machine gun.
T-72 Tanks
The T-72 tank is the second-generation Soviet battle tank. These tanks first entered production in 1971, and they are still rolling off the assembly line. ISIS has an estimated five to 10 T-72 tanks, although it is unknown whether they will be able to keep the vehicles in working order.
The T-72 is heavily armored and features a 125-mm main gun. It is also armed with a secondary machine gun and an antiaircraft gun.
Humvees
ISIS acquired U.S.-built Humvees when it stormed Mosul. The U.S. had provided these same Humvees to the Iraqi Army. The vehicles allow for quick and effective movement across rough terrain.
The Humvee's heavy armor also protects forces against small-arms fire as well as against collateral damage from indirect explosions. The vehicles offer little protection against land mines or buried IEDs.
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