After the outbreak of World War II, Prendergast received a commission with the British Army's
Royal Tank Regiment. Together with his explorer associates he was involved in the formation of the
Long Range Desert Group (L.R.D.G.) under the command of Bagnold. It was thanks to
Ultra and Prendergast and his L.R.D.G. that the Allies were able to hold on to Egypt in spite of heavy armoured reinforcements reaching
Erwin Rommel’s
Afrika Korps through Tunisia, including the much feared
Panzer Mark IIIs and
IVs. After viewing detailed intelligence reports prepared by an embedded L.R.D.G. detachment, Deputy Director of Middle East Intelligence, Major (later Brigadier) John
Enoch Powell concluded that an outflanking movement through the Qattara Depression was highly unlikely, given the terrain and lack of supply infrastructure able to handle heavy matériel. After commanding the L.R.D.G., Prendergast went on to be Deputy Commander of Raiding Forces, and later Deputy Commander of the
Special Air Service Brigade in 1944–1945, and subsequently Commander of the
Free French SAS Regiments, with the rank of
brigadier. For his wartime service he was awarded the
Distinguished Service Order in December 1942, and the Czechoslovak
Order of the White Lion III Class. ==Death==