shoot. i'll help you then. i never studied modern history or whatever, but i know a lot about my country and the neighbouring countries i.e Thailand, Laos, Vietnam.
how does Cambodia get involved/affected in the vietnam war?
King Norodom Sihanouk (nor-ro-dom see-han-nou-k) "k" is used but it is silent
never intended to let Kampuchea (gum-puu-chea) get affected or involved in the Vietnam war.
in the late 1960s...the American & pro-democracy Southern Vietnam government and the Northern Vietnam government broke out in a war.
the Northern Vietnam government want to use eastern Cambodia as a base for their soldiers to rest, and ambush the southern viet soldiers.
the American/South Vietnam wants Cambodia to refuse Northen Vietnam and fight if necessary.
therefore, King Norodom Sihanouk is facing dillema. he is only a new king. not much experience caused him to make mistake later on.
King Norodom Sihanouk see letting Northern Vietnam use eastern Cambodia for a while is safer because he see Vietnam as a close neigbour and very dangerous one if he refuse.
therefore, he let them. America/Southern Vietnam now see Cambodia as enemy and America bombed Cambodia. America bombed Cambodia using as an excuse saying that America is only bombing Viet soldiers but it is actually not, because it is under order of President Nixon to bomb Cambodian people as well.
a lot of fighting are in the eastern Cambodia between Northern Vietnamese and Southern Vietnamese.
western, nothern, southern Cambodia are okay.
in the meantime, while the war drag onto the early 1970s, and then to 1973/4, King Norodom Sihanouk formed a party called Cambodian People Party which later became the Khmer Rouge Party. Khmer (K'my because it is based on French romanisation on Cambodian sounds, not English romanisation) means Cambodian in Cambodian language. Rouge is French meaning red. in Cambodian language, noun goes first and adjective go last e.g. big mountain = mountain big. French language has the same grammer on "noun, then adjective" e.g. femme fatale = woman deadly, in english would be deadly woman.
In 1974, i think, King Norodom Sihanouk thought he will gain advantage of the Cambodian politic and beat Lon Nol's government by using C.P.P but he was wrong. the C.P.P soon turn on him and then King Norodom Sihanouk was held prisoner by them with his family in his royal house. Well, there you go, the Khmer Rouge defeated Lon Nol's American backed government and gained total power in 1975 to 1979.
if got questions, or something help, i'll help. i know some of my writing is a bit messy =/