Such intermittent combat activities have been fueled by the advent of armed drone technology and the propensity of transnational terrorist groups to operate from poorly governed areas or failed states with few or no American troops and no effective local government with a police force , including the tribal region of Pakistan, rural Yemen, and parts of Somalia and Libya.

Drone strikes began under the George W. Bush administration and increased during Barack Obama’s first term, along with political and legal battles over reports of civilian casualties and the deliberate murder of an American citizen suspected of terrorism, Anwar al-Awlaki without trial.

In May 2013, Mr. Obama issued a series of rules regulating such operations and intended to limit their excessive use. It required a high-level review by the authorities to determine whether a terrorist suspect posed a threat to the Americans and “almost certain” that no civilian bystanders would be killed.

In October 2017, Mr Trump replaced Mr Obama’s system with a more relaxed and decentralized system. It allowed local operators to decide whether suspects should be attacked because of their status as members of a terrorist group rather than because of their threat as individuals, and as long as the conditions set out in the general operating principles for the area were met.

Many Obama-era national security officials have returned to the Biden administration with expectations that Mr Trump’s changes will be reversed, at least in part. Still, some military and intelligence professionals have rubbed themselves under Obama’s system and said it was too bureaucratic, according to those familiar with internal considerations.

The Trump administration did not disclose that it had developed a new framework for drone strikes in 2017, although The Times reported its existence and some of its key features at the time. Mr Bossert said that at the time he unsuccessfully pushed for his key parts to be downgraded and made public.

“I suggested releasing relevant parts of the directive from the start,” he said. “My suggestion was not followed. Even so, this debate and our core principles of cherishing innocent life should only ever be open to the light of day, even though they only take the evil. “