Between 30 and 31st July 1945 XE-4 commanded by LEUT M.H. Shean, RANVR was involved in Operation SABRE; the cutting of two underwater telegraph cables off Japanese-occupied Saigon. The Japanese were using the telegraph cables to send messages and these could not be intercepted by the Allies. By cutting the cables the Japanese would be forced to use wireless communications which could be intercepted and decoded by the Allies. Shean designed new grapnels to hook the undersea cables, which Engine Room Artificer Vernon ‘Ginger’ Coles manufactured. On 27 July the submarine HMS Spearhead took XE-4 in tow for the three day transit across the South China Sea.
On the morning of 30 July Shean took over XE-4 from the transit crew and using underwater dead reckoning, updated by occasional sightings of the Cap St Jacques lighthouse, Shean navigated XE-4 into the shallow mouth of the Mekong river where, on 31 July 1945, he began a submarine trawl for the cables. After ploughing the seabed for hours, XE-4 snagged the first cable, and 13 minutes later the diver, fellow Australian Sub Lieutenant Ken Briggs, RANVR returned on board with a short length of cable as proof that it had been cut. Resuming the trawl the second cable was located, much deeper than the first, and Sub Lieutenant Adam Bergius, RNVR cut this cable after several attempts.
Shortly after midnight XE-4 rendezvoused with Spearhead and was towed to Subic Bay. Shean was subsequently awarded a Bar to his DSO ‘for gallantry, perseverance and outstanding skill in successfully cutting the Hong Kong-Saigon and Singapore-Saigon cables on 31st July 1945. The operation was performed in water much deeper than expected and hampered by tide and rough weather’ (London Gazette, 18 December 1945.