A war with North Korea could result in about 10,000 American combat-related casualties in the first few days alone, according to US military planners.

A classified military exercise last week, attended by Army chief of staff General Mark Milley and head of Special Operations Command General Tony Thomas, tested hypothetical scenarios of how US troops would mobilise and strike if ordered to into a potential war, reported the New York Times.

The “tabletop exercise”, held over a few days in Hawaii, thrashed out the challenges that could hamper a US assault on North Korea’s sizeable military.

It determined that US casualties could be amplified by the Pentagon’s limited ability to evacuate injured troops daily, and by the possibility that Pyongyang could retaliate with chemical weapons.

Civilian casualties would far outweigh the initial toll on US troops, and could potentially reach hundreds of thousands, commanders were told.