Initially, local Berliners were wary or even hostile in their attitude toward Noir's work. Some were concerned about the source of his potential financial backing, even suggesting that he might work for the American Central Intelligence Agency or that he might be a French spy. Noir also had to paint quickly and surreptitiously to avoid being caught by the Genztruppen (German Democratic Republic border guards). Owing to these constraints, Noir developed his now iconic style (which he dubbed "Fast Form Manifest") to portray his figures with one continuous line and just a few colours.