I created this account to answer your question. Please have some manners and be civilised.
1. Khmer Rogue was one of a few allies of China at that time. How many allies do you think China had? I can only name North Korean. So of course China supported Khmer Rogue to counter-balance the Soviet-Vietnam Alliance at South East Asia.
2. Towards the end of Sino war, Vietnam gov received support from both the Soviet. At the same time, the Soviet-China relationship went sour. China thought that "if you aren't with us, you are againts us" and from the look of it, Vietnam may join side with the Soviet. So China turned to the US, made deals about Vietnam (without the Vietnam gov knowledge) to receive US support againts the Soviet. The 1979 war was to test if the Soviet could directly have a military intervention in case of another Sino war.
3. As far as I know China had a lot of border clashes with neighboring countries since 1950 (India, CCCP, etc). As for the 1979 war, China prepared for it in 1 year.
4. I admit that 12 years occupation of our troop were a lot. But it is because we did not cleanly wipe out the remaining Khmer Rogue before they fled to Cam-Thai border. Also the US had bases in Thai so you think they would let us come in Thai territory?
5. It's not like Vietnam did not want to erect a communist gov in Cambodia, but the world did not allow it. Our historians now say that at that time, it was like Vietnam againts the world. No one supported Vietnam occupying Cambodia. Even communist friends like CCCP, Cuba, North Korea, Eastern Europe remained silent. A communist gov in Cam would not stand on its own, because US was right next door. Vietnam could not do it alone.
6. I live in the Vietnam-China border region and grow up hearing stories about the 1979 war. I have 2 uncles who were militia at that time. The most common stories I heard is how Chinese troop fought. They advanced in waves, standing tall and walking toward Vietnam positions, only to be mowed down by machine gun fire. If anyone dared to turn back, their comrades would shoot them on the spot. Another common story is of civilians who did not evacuate during the war. Most of them were robbed and beaten by Chinese soldiers, and some were even publicly decapitated or tortured to death. I have my doubt but then, there is no fire without smoke.
And about the destruction of infrastructures, even war cannot justify act of violence towards civilians properties. Destruction of military base? Acceptable. Destruction of schools, hospitals and houses? Unacceptable. If a doctor save someone's life, does he/she have the right to take it?
1. My question is we support Khmer Rogue means we support they killing people and invasion on you? Ok?!
Khmer Rogue is our allies? what's allies, good friendship?! as you logic, USA also our allies at that time, then we had many allies.
2.Still just balame China, hehe, Do you know when Sino-Soviet friendship became bad?
the intension of 1979 war was to test the thing you said? We had clash with Soviet in 1969, why need another one? very ridiculous? hehe, keep making excuse.
3.A lot of clashes with our neighbour counries? how many? with India, Soviet and you vietnam? do you know how many neighbours China has? so what about Vietnam, how many clash did you have with you neighbour?and how many neighbours vietnam has?
just 1 year? not prepared from 1975 now?
4.Excuse is excuse, hehe, I also didn't expect you can tell us your real intention of invasion and occupation to Cambodia.
And fact is your army had enter into Thai territory.
5.Irrelevant reply, I said, you just leave a government that not cruel like Khmer Rogue, you are not that good, your invading to Cambodia is not to help Cambodia, OK.
And, why can't erect a communist government? CCCP silent? why they silent? as you logic, Khmer Rogue was allies of China, they should support you.
6. Story in Vietnam, I didn't expect that these story about China will speak well of China, do you know the story in China about Vietnam about Sino-Viet war? and these story also from soldiers who join that war.
Yes, it was a little violent toward civilians properties, but for Chinese, you vietnamese are shameless and ungrateful, use Chinese selfless aid of weapon and material to invading other countries, even killed our border people and occupied our territories, our donate huge weapon to you, even many soldiers die for your country, send generals to vietnam to fought France and USA with you, why should we leave the thing gave to you? we choose to destroy it or take it back, you didn't pay for it, you don't deserve them.
If that doctor save the guy's life without paying,but that guy think take it for granted, don't know thank the doctor, but frame the doctor, even hit the doctor, for me, doctor taking the thing in his body back can be acceptable, you can ask other doctor cure you, like Soviet, and you vietnam died, because we destroy the infrastructures?
we didn't want kill you, our intention is not, kill a communist country is not in the interesting of China, just let you know, don't mess with us, get your troop out of Cambodia, give up some unrealistic dream, that's all.