Sperrle's air fleet Enigma signals had been cracked and ULTRA codebreakers from Bletchley Park deciphered signals sent by "Luftflotte" 3 headquarters to the OKW. Reading the reports, Allied intelligence deduced that the bombing operations against bridges, west of the Seine, and fighter activity between Mantes and Le Mans, had convinced the air fleet staff the invasion would take place in the Pas de Calais. The air fleet reports, dated 8 and 27 May 1944, expressed the view this activity pointed "unmistakably" towards that conclusion. Operation Fortitude reinforced that belief.