Operation Garlic was an operation to attack the Dortmund-Ems Canal by 617 Squadron carried out on 14-16 September 1943; the operation was unsuccessful as the canal was not significantly damaged by the attack, while 617 Squadron lost six of the nine aircraft and crews involved in the operation.

The Dortmund-Ems Canal was a significant industrial highway, making it a suitable target. It was believed that if several 12,000lb bombs were dropped on the aqueduct at low level then it could be breached. The large bombs used had a poor aerodynamic design. To deliver them accurately they had to be dropped from a low level. For this reason, 617 Squadron was assigned the job of destroying the canal.

The raid was undertaken by eight Avro Lancaster aircraft of 617 Squadron supported by six de Havilland Mosquito aircraft from 418 and 605 Squadrons. The raid was scheduled for the night of 14/15 September; however, the aircraft were recalled whilst over the North Sea due to fog and mist over the target. Whilst returning, Squadron Leader (S/Ldr) Maltby's aircraft hit the sea, possibly after colliding with a Mosquito which was returning from a different raid, and all the crew were killed. Flight Lieutenant (F/Lt) Shannon and his crew circled the wreckage site for two hours waiting for rescue. Maltby's body was the only one recovered.

The attack was re-launched on the night of the 15/16, with the same Lancasters involved, except that F/Lt Martin took the place of Maltby. The point of attack was nearby to Münster where the canal divided into two branches. The attacking force was split into two groups with three Mosquitos for each four Lancasters plus an additional two reserve Lancasters, the main purpose of the Mosquitos being to defend the Lancasters from flak. The visibility on the raid was reported to be very bad, preventing accurate location of the target.

Commander	Returned?	Notes
Wg-Cdr Holden	No	Raid leader. Shot down by flak.
S/Ldr Maltby	No	Deputy Force leader. Crashed on the first attack whilst returning.
F/Lt Knight	No	Aircraft was damaged due to hitting a tree. Was able to allow his crew to bail out; however, Knight was unable to land the aircraft and was killed.
F/Lt Wilson	No	Requested permission to attack; however, nothing further was heard from the aircraft.
F/Lt Allsebrook	No	Dropped load of bombs; however, contact could not be made shortly after.
P/O Divall	No	Heard over the R/T, dropped his bomb, then crashed.
F/Lt Shannon	Yes	Shannon dropped his bomb, which exploded over the Tow Path on the east bank.
F/Lt Martin	Yes	Bombed close to the canal. Took command over remaining aircraft after the rest went down.
P/O Rice	Yes	Could not identify the canal area due to poor visibility so returned.

All Mosquitos returned safely.

The canal was eventually breached the following year. On the night of the 23/24 September 1944 aircraft of 617 Squadron attacked the canal using the more effective 12,000 lb Tallboy bomb, which had a seismic effect that breached the canal. It remained out of service for the rest of the war.