Members of the U.S. Senate are investigating Defense Secretary Pete Hegseth over two main concerns: civilian deaths caused by U.S. military action in Iran, and failures to keep American troops safe during the same conflict. What started as questions about a single attack on a school has grown into a wider investigation into whether the Pentagon dismantled its own safety rules for avoiding civilian harm.

The war in Iran began on February 28, 2026, according to a letter from Senators Elizabeth Warren and Chris Van Hollen to Secretary Hegseth (Warren-Van Hollen letter). By early March, U.S. and Israeli strikes had killed more than 1,000 people in Iran, and around March 10, Hegseth announced that day would be the "most intense day of strikes inside Iran" (AP News). Hegseth had earlier said the war could last eight weeks (AP News).

The push for answers began after a U.S. strike hit a girls' school in Iran. On March 11, 2026, Democratic senators demanded that Hegseth provide answers by March 18 (Reuters). Senator Peter Welch joined 45 senators in pressing the Defense Secretary for answers on the school bombing and civilian casualties, issuing a press release on March 12 (Welch press release). Senators had been expecting a report on the school strike as of March 10 (AP News).

Senators quickly widened their focus beyond the school strike. Around March 9–10, Democratic senators demanded immediate hearings on the war, saying they wanted to bring the conflict to a quick end and protect American troops who had already been hurt (Reuters). About 140 U.S. troops had been wounded by that point (AP News).

On April 19, Warren and Van Hollen led a letter from Democratic senators to Hegseth specifically about civilian harm in the Iran war (Warren-Van Hollen letter). The next day, the two senators opened a new investigation into Hegseth's role in cutting back the military's civilian harm prevention programs (Warren press release). According to their investigation, Hegseth made deep cuts to funding and staffing for these programs, which they say resulted in more than 1,700 civilian deaths (Warren press release).

Separately, Warren, along with Senators Kelly, Gillibrand, and Blumenthal, investigated Hegseth's failure to protect troops in the Middle East after a fatal attack (Warren press release). Warren also led a letter from Democratic senators on protecting service members in what has been designated Operation Epic Fury (Warren letter).

The Senate's investigation now covers three areas that connect to each other: the specific questions about the school strike, the broader rollback of programs meant to prevent civilian harm, and the failures that left U.S. troops vulnerable. Each area generates its own demands for documents and hearings, putting pressure on the Pentagon from multiple directions at the same time.

Congress has several tools it can use to push back: it can hold up the confirmation of Pentagon officials, change the defense budget, and require the military to submit reports. Whether senators actually use these tools to force changes, or whether their letters stay just letters, depends on whether Senate leaders want an open fight with the president's administration while a war is still going on.

The broader question is whether Senate Democrats can stay united across all three investigations, or whether they will split between those focused on civilian deaths and those focused on troop safety. The school strike gave them a clear rallying point. But the dismantling of a program called the Civilian Harm Mitigation and Response Action Plan, or CHMRAP, which was set up under the previous administration to track and reduce civilian casualties, raises a deeper concern. If the systems for preventing civilian harm are taken apart, rebuilding them later is much harder than keeping them in place.

What is not yet clear is whether the Pentagon will meet the March 18 deadline for answers on the school strike, or whether the April letters will produce real responses or silence. Hegseth's eight-week timeline for the war, stated in early March, now sits against a backdrop of growing congressional pressure on how the war is being fought, what it costs, and who is being held accountable.