Was there any way Vietnam could stay independent from French or any other European colonizing effort?
The China takeover idea is also interesting, although not in line with the OP:
It was discussed 13 years ago on SHWI:
https://groups.google.com/forum/#!s.../soc.history.what-if/88eRoq98kNU/TOYRtTMwkzAJ
"Hm. People are forgetting about the nearest imperial power on the
spot, and one with a prior claim to the area as a tributary state:
China.
While China was declining economically -- GDP per capita dropped
about a third from 1800 to 1850 -- and was wracked by British opium
and societal breakdown, its military picked up the pace against non-
Westernized armies rather well. We commemorate this increase in
Chinese military capability every time we eat General Tso's Chicken;
after kicking Taiping ass, General Zuo also put down Muslim revolts
in China's far northwest, and the Nien rebellion, sort of a proto-
banditti state.
By the time of the Sino-French war, the Chinese were even able to
fight the French to a standstill on the Vietnamese border (though
they were hopelessly outclassed in the naval battles; Taiwan was
completely blockaded)."
The removal of a casus belli doesn't mean no colonisation.French Vietnam was basically a ssrie of incident and rash decisions. I can't give the answer this deserves as I'm not on a computer but still.
The Emperor Tu Duc was asked repeatedly by Napoleon III to stop persecuting Christians who were a large minority at the time, Roman Catholic mostly.
After a while the French staged an expedition with the Spanish in the late 1850's to take Danang/Tourane, a major port. This was a failure. They tried to take Saigon as a diversion but it didn't oo much good.
They were only saved by the apparition of the massive french fleet that had participated in the 2nd Opium war. That gave the French Cochinchina.
Twenty years later, Tonkin was turned into a protectorate after the Vietnamese kept persecuting Christians and didn't respect trade treaties.
Lots of pods there. Have the emperors be more concilient toward Christians and there's no casus belli for colonisation
Certainly does not but colonialism has a limited lifespan and this was a casus belli for the French.The removal of a casus belli doesn't mean no colonisation.
Well, OTL Siam avoided colonization because it could act as a buffer between the British and French territories. Could things unfold differently so that Siam is colonized and Vietnam becomes the buffer state between Siam and China?
A Vietnam under Qing direct control could still very much maintain a unique identity. For the Qing to counter European colonialism, the Qing has to first be strong. Being strong also means that the Qing systems established by previous emperors could survive. The Qing practiced the separation of the "peripheral peoples" from the Han in OTL. Since the Viets are different enough from Southwestern tribes like the Zhuang(who were not prevented from intermarrying Han people), they could be treated like the peripheral peoples and have laws that prevent han-viet marriage and cultural exchange. Basically, Vietnam becomes Mongolia.
Not really. IOTL, the Republic of China claims much more land than the PRC. (See: Mongolia, Tannu Tuva, North Burma etc.) But hey, butterflies. However, looking at it from another way, if the Qing manages to be strong enough to conquer Vietnam and hold it (which probably means it has westernized) there might not be a Republic, communist or democratic. Since this Qing dynasty would separate the Viets and Han, I don't think the Viets would resist.particularly any Republic of China.