I do believe someone mentioned in another thread (possibly another site), that the troops will join only if they are of the same culture. Up until my current campaign, I never bribed anyone or anything. Just think it's rather absurd and far too easy. Didn't do it in MTW, neither. Diplomacy isn't great in either game, and I've always found it more realistic to just slug it out.

However, after reading all of the negative aspects of bribing in RTW, I decided to try a campaign called "Bribing for Conquest". Since you need money to test the theory, I chose Egypt. It also helps that they have good troops & good location if you do have to fight. So far, I've "accumulated"--hate to use the word conquer since it isn't appropriate--almost all of Africa, Western Asia, Greece, and a big hunk of Eastern Europe. I've only fought about twenty battles, ALL against faction leaders or heirs whom I couldn't bribe. I stayed nice and peaceful starting out, and concentrated on economy. It's so easy to bribe that it's laughable. And it really isn't expensive. I can generally bribe an army for less than it took the faction to recruit it. I also used the incredibly funny tactic of selling maps to the same factions, year, after year, after year. By the time Rome got to me--I say it that way because every time they started an army my way, I'd use one of my blossoming 8-9 influence diplomats to make them disappear--I'd already taken Greece and was bordering them in numerous locations. Course, if one faction of Rome declares war, they all do.

So, as it stands now, I've almost "obtained" enough provinces to attack Rome for the win. The campaign has been interesting, often funny, but never really in doubt. I've learned two things from this: first, I've never had an army join my command after being bribed, even when the named characters do. Second, this stuff needs to be fixed by CA. Fortunately, campaigning is only single player, and we can play with whatever tactics we choose. I didn't use any of the cheats, because that wouldn't have given me an honest evaluation of the diplomacy in RTW. Looking back, I doubt it would have mattered, anyway. Sad.