Inspired by SavoyTruffle's challenge from earlier today, here goes...
I was reading about the French conquest of Vietnam and Southeast Asia and how a lot of it seemed to have been accomplished by local French officers who didn't have the backing of their governments and were sometimes disowned if their actions proved problematic.
I also read about Liu Yongfu (
http://en.wikipedia.org/wiki/Liu_Yongfu) and the Black Flag Army, a Chinese bandit force from the Taiping Rebellion who imposed a 10 percent toll on commerce on the Red River and inflicted military defeats on the French.
So here's a very bare-bones TL. I think the point of divergence could be the Black Flag army performing better during the Son Tay campaign.
http://en.wikipedia.org/wiki/Son_Tay_Campaign
If the Black Flags receive more Chinese and Vietnamese support, they might do better here AND Yongfu won't be inclined to sit out during the subsequent events where his army could have greatly assisted the Chinese and Vietnamese. Yongfu not sallying and taking heavy losses at Phu Sa might also improve the odds of stalemating or defeating the French. The French were counting on a quick victory in order to present the Chinese with a fait accompli--if this drags on and on, that won't happen.
Basically, the French decide the territory isn't worth the effort and there is no Sino-French War. The French retain control of southern Vietnam (Cochin China) and thereabouts, while northern Vietnam (Annam and Tonkin) is recognized as belonging to the Nguyen dynasty, vassals of Qing China. Yongfu ends up establishing his own personal dynasty in OTL Laos--apparently the Laotians came under French protection in order to avoid his attacks--as a vassal of the Qing. Not sure what will happen to Cambodia--maybe they'll end up being French vassals anyway for fear of the Thais.
The French colonize Cochin China more intensely and we have more spread of Catholicism and French culture and more racial mixing. Eventually, we end up with southern Vietnam becoming something completely different culturally from the rest of the country.
Come WWII (assuming minimal butterflies) the Japanese could try to curry favor with the Nguyen dynasty and allow them to reimpose their rule on Cochin China. Given how anti-Christian the Nguyens could be and the grotesque brutality of the Japanese, this could get downright nasty. Furthermore, brutalizing a population can produce national feeling/identity--De Gaulle warned the Israelis not to occupy the West Bank or they'd create a Palestinian nationalism--that would make it even harder for the Nguyens to reassert control.
Assuming WWII ends per OTL, the Japanese will be tossed out and the Nguyens discredited (seriously, did anyone in OTL really like Bo Dai?) and a new government, which might be a new dynasty to supplant the Nguyens or something different like Communism, would take power in the north. I would imagine they too would want to to reclaim the south.
Meanwhile, the French would have more popular support for maintaining their rule in southern Vietnam, unless "Cochin Nationalism" gets really anti-French for abandoning them or something.
Basically, TTL's 1950s will see a dying French Empire either trying to maintain control of southern Vietnam or establish a pro-French successor government. Meanwhile, you have a North Vietnam bent on reclaiming control of the south, a wild card Yongfu dynasty in Laos that might be facing unrest by subugated Lao and would also have to deal with whoever is in charge of China.
The situation in continental Southeast Asia might in turn affect Indonesia. If the French retain control of southern Vietnam or at least Hong Kong-like enclaves in Saigon or Cam Ranh Bay, the Dutch might try to stay in control of parts of the Dutch East Indies (the Moluccas?), which might lead to the balkanization of the area.
No unified Indonesia intent on "crush(ing) Malaysia" could lead to more attempts by the Malaysians to assert control over Singapore. IIRC the reason for Singapore's relative militarization is fear of the more numerous and conquest-minded Malays. In TTL, we might see one or more attempts by the Malays to conquer Singapore.
And then there's the Cold War, with the U.S. and USSR having their own pet factions...
What do you all think?