Political battle lines are forming ahead of Congress’s first public oversight hearing to scrutinize senior military leaders’ recommendations to the White House in connection with last month’s calamitous exit from Afghanistan, as lawmakers in both parties pursue accountability for the loss of life and failure to evacuate everyone who wished to leave.

Senate Republicans have seized on a disclosure from Army Gen. Austin “Scott” Miller, commander of U.S. forces in Afghanistan from 2018 until his departure in July, who told the Senate Armed Services Committee on Tuesday that before President Biden announced his decision in April to pull out all military personnel, the general had advised superiors to leave a few thousand troops rather than complete a full withdrawal. Democrats left the session frustrated so many people were left behind and seeking a sweeping examination of the 20-year mission.

The response to Miller’s testimony, delivered in a private briefing for the committee, has foreshadowed the tense reception that awaits Defense Secretary Lloyd Austin, Joint Chiefs Chairman Gen. Mark A. Milley, and U.S. Central Command chief Gen. Kenneth “Frank” McKenzie when they appear on Capitol Hill on Sept. 28.

“The president wasn’t there, but [Miller] did talk to Austin, McKenzie and Milley, and told them that he had been opposed to the total withdrawal,” Sen. James M. Inhofe (Okla.), the committee’s top Republican, told reporters after Miller’s testimony had concluded. “We heard enough to know that there are inconsistencies between what the administration has said and the truth. Clearly, President Biden didn’t listen to all the military advice.”

Miller told the committee that he could not verify whether his recommendation made it to the White House, said an official familiar with the general’s testimony who, like others, spoke on the condition of anonymity because the matter remains highly sensitive. A separate official said Friday that Miller’s position was conveyed to Biden.

The Pentagon declined to detail what others advised the president, and the White House did not return a request for comment.

“The Secretary is more than comfortable with the degree to which senior defense and military leaders contribute to the policy-making process,” Pentagon spokesman John Kirby said in a statement. “We won't detail the specifics of their advice, but their counsel was fully considered.”

President Biden addressed the nation on Aug. 31, defending the U.S. evacuation effort in Afghanistan. (Mahlia Posey/The Washington Post)

In public statements, Biden has said that the generals were “unanimous” in their assessment that the military should complete its withdrawal by the end of August. But that became the case only after Biden announced his decision to leave despite their recommendations to stay, numerous officials said.

Early this year, Miller cautioned senior U.S. officials that the Kabul government’s fall could come rapidly after a U.S. military withdrawal, according to two officials familiar with his thinking. The general raised concerns publicly and privately about a wave of attacks against Afghan troops and targeted killings of Afghan leaders, and advised privately that the violent conditions did not support the continued withdrawal of U.S. troops that began during the Trump administration.

Miller and McKenzie were aligned in much of their analysis, these people said. Austin and Milley also recommended against a complete withdrawal, numerous U.S. officials have said. But it’s unclear if they saw the situation in the same stark terms. Milley, speaking alongside Austin last month at the Pentagon, said that no one in the U.S. government knew that the Afghan government would collapse as quickly as it did.

Miller spoke with Biden via teleconference once, during the spring, before any decisions regarding the withdrawal had been finalized. When it was clear the president intended for the military to leave, however, Miller advocated it be done swiftly, believing that approach to be the safest for U.S. troops whom he feared would be vulnerable to attacks.

The initial plan, according to an official familiar with Miller’s thinking, was to leave via Bagram air base — which was, for many years the American military’s nerve center located north of Kabul — and to extract all personnel by July 4. But as the Taliban took back key cities and provincial centers, the administration adjusted course. Bagram was left open, but only for a few extra days, and the Biden administration also decided to leave about 600 U.S. troops in Kabul to protect the U.S. Embassy and Hamid Karzai International Airport.

Miller left Afghanistan on July 12, handing his duties to McKenzie. A month later, the Afghan president fled the country and the Taliban swept into Kabul — disproving American leaders’ belief that it could take months before the capital fell.

The U.S. military scrambled to organize a massive evacuation, sending thousands of troops back into Afghanistan to help carry out the airlift of tens of thousands of U.S. citizens, foreign nationals, and Afghans, as massive crowds swarmed the perimeter desperate to get inside and onto planes carrying people to safety. Amid the chaos, some holding paperwork to be flown out were instead turned away at Taliban checkpoints. A suicide bomber exploited the situation, killing 13 U.S. service members and at least 170 Afghans in the waning days of the operation.

The Biden administration has sought to frame the evacuation mission as a success, pointing to the more than 123,000 people who were airlifted out of Kabul’s airport in two and a half weeks. But the president’s critics, especially those in the GOP, have faulted his administration for leaving behind American citizens, legal permanent residents, and holders of special immigrant visas. Some have called on Austin and Secretary of State Antony Blinken to resign.

Milley also has faced calls for his ouster, after a series of new revelations regarding contacts with his Chinese counterpart during the waning days of the Trump administration — conversations Milley and other Biden officials have defended as legitimate. Against that backdrop, the political intrigue over what he, Austin, and McKenzie recommended to Biden concerning the Afghanistan withdrawal — and whether it reflected the doubts of their subordinates in theater — threatens to overshadow what was expected to be a bipartisan reckoning.

Both Democrats and Republicans have raised concerns over how the military will conduct “over the horizon” missions to counter terrorist threats in Afghanistan going forward — a concern revived Friday with the military’s acknowledgment it killed innocent bystanders in an errant drone strike amid the evacuation chaos — and they want to know why so many American citizens, legal permanent residents and Afghan holders of special immigrant visas were left behind once the Taliban took over in Kabul.

Some Democrats’ patience with the Biden administration has begun to wear thin, as they question how the government plans to extract their constituents and their relatives who remain in harm’s way. After hearing from Miller, Sen. Richard Blumenthal (D-Conn.) said it had “only deepened my dismay and anger about the confusion and chaos in failing to evacuate Americans and Afghan allies who are now stranded and caught at great risk.”

But seeking answers about tactical failures means walking a political tightrope. Democrats want to scrutinize not just the blunders of the last several weeks, but nearly all 20 years of decision-making that led to the point where the United States had to relinquish Afghanistan to the Taliban — much of which took place under Republican presidential administrations.

There is a growing sense on Capitol Hill that neither the military that prosecuted the war, nor the lawmakers who conducted oftentimes passive oversight amid a climate of worsening partisan politics, can be trusted to undertake that task themselves.

There have been bipartisan calls for an “independent” investigation in recent days, and the House has included a provision in its annual defense authorization bill for a 12-person outside commission to do a full assessment of America’s longest war. The bill is expected to be voted on in the House next week.