In World War Two, US generals were concerned about working alongside British forces, because a British general is a higher equivalent rank than a US general. They were going to change the US designation to "field marshall", so that there'd be less confusion about who was the leader of each force. But this was opposed by a certain US general who didn't want to become "Field Marshall Marshall".
It's strange... during FFVII, Reeve appears to be a very senior member of Shinra's management, even though he's officially the "Director of Urban Development", yet he also wears a Turks uniform. I'm guessing that, by the time FFVII begins, he's no longer an operational member of the Turks, and has branched out into intelligence-related activities in other Shinra areas. Urban Development can be closely tied to monitoring and screening the population, so he might be handling that...
He seems to be a central figure in Before Crisis, maybe that game will explain how and when his sense of morality drove him away from the Turks work carried out by the likes of Reno, Rude, Elena and Tseng...