Yemen spiraled further into chaos on Wednesday night, with a Saudi Arabia-led Arab coalition launching a military intervention marked by airstrikes by dozens of fighter jets and the deployment of thousands of ground troops and tanks on its Yemeni border. U.S. officials said they will offer intelligence and logistical support to the Saudis, but that’s really only a piece of it: The Saudi military is equipped with billions of dollars in advanced American-made weapons.

Between October 2010 and October 2014, Washington and Riyadh reached more than $90 billion in weapons deals, according to a report published in January by the Congressional Research Service. The sales have included everything from war planes to armored vehicles, along with powerful missiles and bombs.

“In spite of apparent differences of opinion over regional developments, U.S.-Saudi security cooperation continues to anchor official bilateral relations as it has for decades, bolstered by major new arms sales, continued security training arrangements, enhanced counterterrorism cooperation, and shared concerns about Iran, Al Qaeda, and, more recently, the rise of the group known as the Islamic State,” the report said.

“The latter group’s military advances in Syria and Iraq appear to have generated serious concern among Saudi officials, as have reports that suggest popular support for the group may be strong among a small, but potentially dangerous minority of Saudis,” the report adds.

Saudi officials said Wednesday that they had deployed 100 fighter jets over Yemen as they sought to drive back Shiite rebels who have forced Yemen’s president, Abed Rabbo Mansour Hadi, to flee into hiding. Many of those are likely to be F-15SA fighter jets, a configuration of the American-made F-15E Strike Eagle, which the U.S. Air Force continues to fly regularly in airstrikes against Islamic State positions in Iraq and Syria.

The Saudis reached a $29.4 billion deal with Washington in 2010 for the sale of 84 new F-15SA fighters and the upgrade of 70 older F-15S fighter jets. The deal also  included thousands of bombs to be loaded on the planes, U.S. military officials said at the time.

The United States also reached a separate $25.6 billion deal in October 2010 to send 36 AH-64D Apache attack helicopters, 72 UH-60M Black Hawk helicopters, 36 AH-6i light-attack helicopters, and 12 MD-530F light-turbine helicopters to the Saudis. The companies involved included Boeing, Lockheed Martin, Sikorsky Aircraft, MD Helicopters, General Electric and Longbow. Separately, another $5.5 billion in deals were reached to send Apache Longbow helicopters to the Saudi army and Royal Guard, the Congressional Research Service said.

Both Saudi F-15s and attack helicopters have been used against the rebels in Yemen, known as Houthis, before. In 2009, the Yemeni government launched Operation Scorched Earth, an offensive in northern Yemen with Saudi help, to take on the rebels. Media reports cataloged by the American Enterprise Institute, a Washington think tank, describe a series of clashes along the Yemen-Saudi Arabia border and the rebels used a variety of guerrilla tactics, including rigging animals with booby traps to attack Saudi soldiers.

The United States also has sent night-vision equipment, Howitzers, Humvees and TOW missiles to Saudi Arabia in recent years.

“Saudi Arabia has close defense and security ties with the United States anchored by long-standing military training programs and supplemented by ongoing high-value weapons sales and new critical infrastructure security cooperation and counterterrorism initiatives,” the Congressional Research Report adds. “These ties would be difficult and costly for either side to fully break or replace.”