US marks 21st anniversary of 9/11 terror attacks

Americans are remembering 9/11 with moments of silence, readings of victims' names, volunteer work and other tributes 21 years after the deadliest terror attack on U.S. soil.

Victims' relatives and dignitaries will convene Sunday at the places where hijacked jets crashed on Sept. 11, 2001, the World Trade Center in New York, the Pentagon and a field in Pennsylvania.

Pentagon reveals plan for civilian casualties policy: "Collateral damage" reduction

The directive contains 11 major objectives. They are aimed at helping commanders better understand the presence of noncombatants before any operations begin, and they require operators to consider potential consequences for civilians in any combat action, thus reducing "collateral damage".