 To assist in transporting the Commandos , 12 motor launches ( ML ) were assigned from the 20th and 28th Motor <unk> flotillas . These boats were re @-@ armed with two Oerlikon 20 mm guns mounted forward and aft to complement their twin Lewis guns . At the last minute another four MLs were assigned from the 7th Motor <unk> flotilla ( see <unk> for flotilla details ) . These four boats were also armed with two torpedoes each . Instead of transporting the Commandos , these boats were to engage any German shipping found in the estuary . All the MLs had a 500 @-@ gallon auxiliary fuel tank fixed to the upper deck to increase their range . The S class submarine HMS Sturgeon would leave before the rest of the convoy and be in position to act as a navigational beacon to guide the convoy into the Loire estuary . 
