Thread by @SeaSpitfires

US Patrol-Torpedo Boat PT 509 (left) stands by USS Tide after she struck a mine off Utah Beach on 7 June. Two months later, PT 509 would herself be sunk. 📷Naval History and Heritage Command 80-G-651677

One flotilla of PT boats participated in D-Day & 2 more became operational very soon afterwards. Operating from Portland the 33 boats worked alongside the more numerous Motor Torpedo Boats of the Royal Navy & Royal Canadian Navy in the English Channel. 📷Library & Archives Canada

Portsmouth Command fielded no less than 14 flotillas of Coastal Forces during the Battle for Normandy. Their boats shielded the flanks of the invasion forces on D-Day and guarded the swept channels to the beaches for the weeks afterwards. 📷IWM A24047

Other flotillas operated off the key German held ports of Cherbourg and Le Havre. Operating at night and guided by radar equipped control frigates, their task was to intercept enemy vessels before they could approach Allied convoys. 📷IWM A 24045

Their primary foe were the 4 flotillas of schnellboote stationed on the Channel coast. But throughout spring 1944, Coastal Forces had ground down the Kriegsmarine so that their flotillas were only part operational, and they would shy away from combat with smaller numbers of MTBs.

There were almost nightly engagements between the MTBs and the S-boats in June. These actions could be short, but bloody. But Coastal Forces kept the enemy torpedo boats away from the convoys.

Other MTBs were used as minelayers. In May and June, the 14th & 64th MTB Flotillas laid nearly 500 mines, mainly in Scallops Plus.

Their level of success could be measured in the damage they inflicted on enemy shipping, versus the limited damage the S-boats inflicted on Allied convoys. These reports need more analysis, but the difference is clear.

But Coastal Forces suffered heavily too. 9 MTBs and MGBs were lost between June and August and dozens were damaged, some severely enough to be taken out of commission for lengthy repairs. 74 MTBs were available for service on 5 June, down to 40 on 28 August.

Several PT boats were damaged in the summer of 1944, one severely. But only PT 509 was lost, in an action off the Channel Islands in the early hours of 9 August. She was destroyed with the loss of her entire crew. There is a memorial to them at Noirmont Point in Jersey.