I tried playing the game from 1180 AD to see how well I would do in dealing with the barbs. I was able to wipe them out completely in 6 turns without losing a single city and by losing only a few units (probably about 5 but I didn't count). This may look impressive but it should be kept in mind that I had read the preceding discussion plus Duke's log and I used his brilliant idea of sending a a ship to reach the central stack of barbs (which I killed in 1240 AD). I also played 'globally' i.e. paid attention to the other cities although I wasn't as careful as I would have been had this been the 'real game'.
Here is the log. I hope I'm not wandering too much off topic by showing this 'parallel universe':
1180 AD (0): IPRB trireme in Hangchow, diplomat in Shanghai, crusader in Chengdu, crusader in Tientsin, diplomat in Tatung, diplomat in Kaifeng (hoping the barbs are stupid and do not capture the city), crusader in Capua, diplomat in Genoa. Switch to Leo in Tsingtao.
1200 AD (1): Barbarians do not capture Kaifeng ??! Several of them next to Kaifeng and Tientsin. Crusader in Tientsin kills two barbarians. Horseman bribed for $41, he then kills one barbarian. Now no barbarians can attack Tientsin next turn. Horseman bribed for $41 near Kaifeng, the horseman then kills a chariot and horseman. Now the barbs shouldn't reach Kaifeng next turn. Dips from Genoa and Tatung head for Tientsin as well as a crusader from Capua. Hangchow's trireme heads for the barbarian central stack loaded with a diplomat and crusader (the crusader is a 'backup unit' in the unlikely event that a bribed unit fails to kill the barb stack). We refuse to give invention to the Zulus but still get $50 from them. We get navigation from the Vikings in exchange for theology. The Vikings want $328 (50% of our cash) for continued alliance, we refuse and nothing happens. No gifts from them. IPRB crusader 'from scratch' for $150 in Kaifeng. RB Leo in Tsingtao for $144. RB barracks in Tientsin 'from scratch' for $160.
1220 AD (2): The two horsemen bribed last turn killed. Vikings start Bach. The situation following this:
Tsingtao builds Leo, Mongols abandon it. Crusader in Kaifeng kills two horsemen. Bribe two chariots for $122 after making sure the diplomat didn't move to the square of the latter one. These bribed unit kill two barbs, one retreats to Kaifeng, the other one is in grave danger but the dip is safe. Chariot bribed for $61 near Tientsin, used to kill a horseman that otherwise would attack Tientsin next turn.
1240 AD (3): The sitation at the start of the turn:
Bribe horseman next to central stack. If it fails to kill the stack the dip next to Kaifeng will board the trireme and bribe a chariot next turn. There's also a crusader aboard the trireme. WOOOHHHOOOOOO !!!!! Bribed horseman kills 73 units !!!!!! Then the horseman kills a chariot. The brave diplomat and horseman will die next turn. Now the only thing that is left is to mop up. Tientsin crusader kills a barbarian horseman that could have attacked next turn. Tientsin mostly out of danger now and switches from crusader to settler !
1260 AD (4): Only 9 barbs left at the start of the turn:
Chariot S of Tientsin bribed for $61, then kills two barbs. Crusader in Tientsin kills a chariot. Crusader near Kaifeng kills horseman NW of Kaifeng. Horseman next to Kaifeng bribed for $41, then kills the chariot. Crusader from caravel kills horseman on the coast. Only one barb left.
1280 AD (5): Only one remaining barb:
Crusader kills the remaining barbarian chariot. NO MORE BARBS !! Kaifeng settler unloaded from caravel to build road where the barbs appeared.
In retrospect I overreacted slightly to the barbarian attack since rush buying dips and crusaders in all four of Genoa, Tatung, Cremona and Capua was not necessary. However, I wanted to have some 'redundancy' in my plan, for example the crusader aboard the trireme.