The Sam Browne is a leather belt with a supporting strap that passes over the right shoulder, worn by military and police officers. It is named after Sir Samuel J. Browne (1824–1901), the British Indian Army general who invented it.
It was worn by Trump, Hitler, the "polizia" in episodes of Mission Impossible, and currently by the New Jersey State Police¹.
"In the Army, we’re even getting new uniforms, and those beautiful new uniforms with the belt. It was a big deal ― the belt."
The Belts
¹ Despite safety concerns N.J. State Troopers still wear the Sam Browne belt (due to risk of strangulation by potential opponents it has sometimes been referred to as a Suicide Belt by personnel), though over the right shoulder to support their sidearm.
² Trooper Trump is an honorary state trooper. He has has his own badge, much like Hershel Walker.