McLaurine Pinover, a spokeswoman for McCaul, said the subpoena for the cable, which was sent via a “dissent channel” that allows employees to convey information to senior agency leaders that differs from those of other department officials, was transmitted Tuesday morning.

Secretary of State Antony Blinken, speaking to lawmakers last week, indicated his unwillingness to provide Congress the cable because, he said, it could discourage workers from using the channel in the future. He noted that the department had sent lawmakers thousands of pages of documents related to the withdrawal, which was widely seen as a chaotic and embarrassing end to the United States’ two decades in Afghanistan.he State Department has proposed instead speaking with lawmakers about the document’s contents.

“The department followed up with the committee to reiterate its willingness to provide a briefing about the concerns raised and the challenges identified by Embassy Kabul, including in the dissent channel,” State Department spokesperson Vedant Patel said in a statement. “The committee chose instead to issue a subpoena.”

It was not immediately clear what steps McCaul, who last year released a report on the administration’s management of the withdrawal, may take to enforce the subpoena.

“We have made multiple good faith attempts to find common ground so we could see this critical piece of information,” McCaul said in a statement ahead of the subpoena’s delivery. “ … The American people deserve answers as to how this tragedy unfolded, and why 13 U.S. servicemembers lost their lives.”

Legal experts say Congress has limited power to force an executive branch agency to hand over a document in such situations. Lawmakers could pursue criminal contempt charges or take other legal actions to try to compel the department, but that would be a slow process with an uncertain outcome. Alternatively, they might attempt to force the department’s hand by withholding funds or blocking approval of agency nominees.

“The State Department, for better or worse, as a practical matter has the upper hand,” said Brian Finucane, a former State Department attorney who is now a senior adviser at the International Crisis Group.

Experts say the incident highlights a contested area of executive and legislative branch authorities, one that has never been settled in U.S. courts. It echoes some of the challenges that Democrats faced during the Trump administration in obtaining information from executive agencies including the State Department.

“I will say that it’s difficult to square what might be the legitimate policy-based rationale of the department to preserve the dissent channel with Congress’s oversight responsibilities and its need for information from the department,” Finucane said of the standoff.

The senior Democrat on the committee, Rep. Gregory W. Meeks (D-N.Y.), told Blinken last week that he had also requested the cable last year.

Durakoglu said that the department had conducted numerous briefings on Afghanistan and had provided lawmakers documents including the Kabul embassy’s emergency plan and 300 pages of “sensitive cables” related to the withdrawal. She said the department would provide lawmakers access to a classified review of what occurred during the evacuation by mid-April.

During Blinken’s testimony last week, Republican lawmakers complained that some of the documentation provided by the State Department was so heavily redacted that it had been rendered useless.