 As it turned out , the relationship between SHAEF and Field Marshal Sir Bernard Montgomery 's 21st Army Group was far from cordial , with the Deputy Supreme Commander , Air Chief Marshal Sir Arthur Tedder , and the Deputy Chief of Staff , Lieutenant General Frederick Morgan , both frequently critical of Montgomery . In September 1944 an intelligence crisis similar to Kasserine arose , when the cryptanalysts at Bletchley Park did not locate the 9th SS Panzer Division Hohenstaufen and 10th SS Panzer Division Frundsberg in the Arnhem area , but information from the Dutch resistance and a consequent photo reconnaissance ordered by Major Brian Urquhart , the Intelligence Officer at I Airborne Corps , confirmed the German presence . Strong and Smith then flew to Brussels to warn Montgomery . However , Montgomery decided to accept the risk rather than alter the plans for Operation Market Garden . 
