KABUL—The Taliban's weekend assault on a major coalition base was one of the most determined and effective in the Afghan war, according to details released Sunday, resulting in the biggest single-day loss of U.S. combat aircraft since the Vietnam War.

In addition to the Taliban raid, which killed two U.S. Marines after it began Friday night, two separate insider attacks by Afghan service members elsewhere claimed the lives of six coalition troops. A lethal coalition airstrike that caused a number of civilian casualties, meanwhile,...