Glennon continued to operate in the Mediterranean Sea and returned to New York on 3 December 1943. The destroyer then made two round-trip convoy escort voyages to the British Isles and one to Gibraltar. She arrived in New York from Gibraltar on 22 April 1944, and stood out of that port on 5 May with a task group which arrived at Belfast, Northern Ireland, on the 14th.
Invasion of Normandy and sinking
Assigned to Assault Force"U" of the Western Naval Task Force, she arrived in the Baie de la Seine, France, on 6 June. After patrolling around the bombardment group for submarines and fast Germantorpedo boats, she joined in gunfire support of troops ashore.
Glennon after hitting a mine on 8 June 1944.
On 7 June, she fired 430 5-inch (127mm) shells ashore in support of troops advancing north toward Quinéville. She was again approaching her gunfire support station at 08:30 on 8 June, when her stern struck a mine. A whaleboat picked up survivors while minesweepersStaff and Threat arrived on the scene, one passing a towline while the other swept ahead of the damaged destroyer. The destroyer escortRich closed in the wake of the minesweepers to assist, then felt a heavy explosion as she slowly rounded Glennon's stern to clear the area. Minutes later a second explosion blew off a 50-foot (15m) section of Rich's stern, followed by a third mine explosion under her forecastle. Rich sank within 15minutes of the first explosion.
The minesweeper Staff found she could not budge Glennon, whose stern seemed to be firmly anchored to the bottom by her starboard propeller. Most of her crew boarded Staff, and those remaining on Glennon lightened her stern by pumping fuel forward and jettisoning depth charges and topside gear. On 9 June, salvage equipment was assembled, and some 60officers and men of Glennon came back on board. The following morning a German shore battery near Quinéville found the ships range. A second salvo hit Glennon amidships and cut off all power. After a third hit, the crew was ordered to abandon ship and the men were taken off in a landing craft. Glennon floated until 21:45, 10 June 1944, then rolled over and sank (location: 49°31′15″N001°09′16″W / 49.52083°N 1.15444°W / 49.52083; -1.15444). She suffered 25lost and 38wounded.