One, the Polish spy Roman Czerniawski, had already changed sides twice before he was brought into the double cross team.
Indeed, Stalin was better informed about the double cross system than Churchill himself.
Without that break, the double cross deception plan which ensured the success of the D-Day landings could never have gone ahead.
A betrayal or cheating of one's own colleagues; an act of treachery, often in an illicit transaction: The two suspected dealers were planning a double-cross
: I would never double-cross a pal
[1834+; fr the reneging on an agreement to lose, a cross, by actually winning]