You'll have to research all the way back to ancient China to know all of those reason; which will most likely mirror most any old civilization. However, for the recent 19th & 20th centuries, Vietnam (Indochina) began their resistance in the 1860's against the French, with some Chinese intervention as well, and maintained their mind-set on a resistance to foreigners ever since those times.
WWII in 1940 simply gave the Vietnamese people "an out" (an opportunity) get rid of foreigners. When Japan came in, that got rid of the French. When Japan left, the French tried to return...the Viet Minh resisted that return. After 9 years, the French left permanently. Then came the Americans...
If you mean 'overnight' you must either break the law, get married or meet her outside of vietnam.
Agent orange
The US .
WW2 set the stage
the vietnamese resistance to chinese crossed both class and gender barriers....lol I have no clue I'm on the same question as you :(
Unlike the invading foreigners they didn't enjoy killing
The Viet Minh .
The legacy left on other Australians by Ned Kelly, an Australian bushranger, was resistance to British colonial ties.
Alexander de Rhodes used Roman Alphabet to create a language first called "National language". Before it was created, Vietnamese used Mandarin, Cantonese,... During the communist government's time, chairman of the country Ho Chi Minh encouraged National language to be spoken as Vietnam's official language, and it remains the official language until now. It was called Vietnamese by foreigners.
The mind-set of European superiority.
In their history, the Vietnamese were able to defeat many major powers of the world - China, the Mongol Empire, France, and the USA. Those deeds speak huge volumes for their fierce drive of independence and resistance determination.
Historical IdentityVietnam, like most Southeast Asian countries is a natural nation-state. This means that because of a long history of centuries (nearly 1000 years) defending a particular set of borders and establishing a particular national identity, the concept of a "Vietnamese Nation" was more or less universally accepted both by Kinh People (the ethnic majority of Vietnam), by Non-Kinh who had historically been part of Vietnam, and by Non-Kinh who were outside of Vietnam, like the Cambodians, Laotians, and Thais.What really led to the development of the Vietnamese identity was the constant attempts by China to invade and overrun Vietnam. This created a strong level of patriotism and a unique identity as the "resistance to the Chinese". (Such kinds of resistance-based identity are common and very powerful, such as the Irish Identity, the Kosovar Identity, the Indonesian Identity, and the US Identity.) When compared to the neighboring Laotians and Cambodians, the Vietnamese embrace of more Chinese-style religion (Daoism, Ancestor Worship, and some aspects of Buddhism), made the Vietnamese distinct from the Theravada Buddhism that prevailed among the other two groups.Modern VietnamModern Vietnamese nationalism and the communism is a direct result of resistance to the modern French Occupation in Indochina. Ho Chi Minh and other Vietnamese saw communism as a form of liberation for the Vietnamese people who had been ravaged by the exceedingly capitalistic removal of their resources for the French industrial machine. The First Indochina War, when Vietnam pushed for independence from the French led to the cultivation of a new Vietnamese resistance-based identity on top of the resistance to China. After this, the war between North Vietnam and the United States, in order to reunify the country, also led to a surge in nationalism and a strengthening of the Vietnamese identity.