The United States has spent $22.76bn in support of Israel’s war on Gaza and operations against the Houthis in Yemen, according to a report by Brown University’s Watson Institute.

The $17.9bn in military aid to Israel since the war in Gaza started a year ago is the highest annual total ever, according to the report.

The aid to Israel is a mix of military financing, weapons sales, and transfers from US weapons stockpiles, according to the report, which is part of the institute’s Costs of War project.

A large part of the US-delivered arsenal is munitions, the report said, including artillery shells and 2,000-pound (907kg) bombs.

Unlike the US’s publicly documented military aid to Ukraine, details of some US military shipments to Israel are more elusive, so the $17.9 bn figure is incomplete, according to Brown researchers.

They cited US President Joe Biden’s administration’s “efforts to hide the full amounts of aid and types of systems through bureaucratic maneuvering”.

Israel, the US’s strongest ally in the Middle East, is the biggest recipient of US military aid in history, taking in $251.2bn in inflation-adjusted dollars since 1959, according to the report.

Even so, the $17.9bn spent since October 7, 2023, in inflation-adjusted dollars, is by far the most military aid sent to Israel in one year.

In addition to the aid to Israel, the US has also spent $4.86bn on operations in Yemen and elsewhere in the Middle East. The US, along with the United Kingdom, has been conducting air attacks on Houthi positions in Yemen since January after the rebel group began attacking shipping in the seas around the country. The Houthis say those attacks target shipping linked to Israel, and are in support of Palestinians in Gaza.

The funding for Israel’s war has increasingly divided Americans due to the mounting civilian death toll in Gaza and Lebanon, with weapons experts pointing to US-funded munitions likely used by Israel’s military to hit tent camps and schools.

In July, 12 former US government officials warned that US arms shipments to Israel were making the country complicit in the destruction of Gaza.

“America’s diplomatic cover for, and continuous flow of arms to, Israel has ensured our undeniable complicity in the killings and forced starvation of a besieged Palestinian population in Gaza,” said the officials, including former members of the US State Department and military, in a joint statement.

While occasionally raising concerns over Israel’s war conduct and briefly pausing the flow of some heavy bombs back in May, Biden has firmly backed Israel’s war effort and refused to put conditions on US military aid.

“No administration has helped Israel more than I have,” the US president said on October 4.