Information borrowed heavily from wiki: https://en.wikipedia.org/wiki/Cambodian_campaign
As of early 1970, Cambodian discontent with the heavy Vietnamese presence in the eastern portion of the country had built up to explosive levels, leading to mass demonstrations by urban and educated Cambodians.
While monarchical head of state Prince Sihanouk was on holiday, the government of his appointed Prime Minister, Lon Nol, supported and sponsored these demonstrations.
Per wiki:
The PoD is something happens between March 12th, and March 18th to prevent the next dramatic event that occurred in OTL:
As we can see, the conflict between Sihanouk on the one hand, and Prime Minister Lon Nol and Cambodian Assembly on the other hand escalated from zero to 60 MPH super-fast, became irrevocable, with Sihanouk and Lon Nol immediately condemning each other to death, and caused Sihanouk to do a complete 180 in his attitude toward the Khmer Rouge, who had killed members of his family previously.
The difference in this ATL* is Lon Nol, while still pushing his anti-North Vietnam agenda as far as he can take it, ultimately accepts Sihanouk is an indispensable figure, who can ruin everything if not brought on board. So, Lon Nol restrains his own anti-Sihanouk allies and sympathizers within the anti-Vietnamese movement in the National Assembly, and prevents them from meeting to hold a vote to oust Sihanouk. He also frantically messages Sihanouk to update him on the crisis and urge the necessity of him coming home to listen to the people's demands as the only way to calm things.
Based on news updates from Cambodia and frantic phonecalls from Lon Nol, reinforced by calls from royal relatives that Lon Nol encourages, Sihanouk speeds drastically speeds up his itinerary, making a brief office call with either Kosygin or Brezhnev or possibly even Soviet Foreign Minister to convey the message, "restrain the Vietnamese" and flying on to Beijing to do the same thing with Mao or Zhou Enlai or Lin Biao and then flying home.
When he arrives home I imagine he would try defuse tensions with the Vietnamese or certainly not order Cambodian forces to escalate things by trying to take material action to follow the departure ultimatum, but he will also be seeing the national fervor to stand-up the Vietnamese. He can mobilize peasant demonstrations in support of himself, and possibly dismiss Lon Nol, but it won't organically make the anti-Vietnamese frustration die-off.
So, what does Sihanouk do in terms of accommodating popular anti-Vietnamese sentiment vs. ignoring it? And pressuring the Vietnamese to reduce their footprint and visibility on Cambodian territory, vs. tolerating their presence. Reopening the port of Sihanoukville would be seen by the urban public as a very provocative move, at least if there is visibly Communist controlled and Communist helpful traffic emanating from there, so Sihanouk would be wise to leave that alone.
And what will the pattern of covert and overt US military activity, in the air, and potentially on the ground, over and in Cambodia be in 1970? Although in OTL, the overthrow of Sihanouk and Lon Nol's open anti-communist stand, and the outbreak of direct Cambodian - North Vietnamese fighting all strengthened pro-invasion of Cambodia arguments within the Nixon administration, according to Stanley Karnow, "[e]ven before the coup against Sihanouk, Nixon was inclined to invade Cambodia."
Would the US and ARVN do an invasion of Cambodia in 1970, or any time? Would Sihanouk come to fight the North Vietnamese, leading the latter to support the Khmer Rouge? Or would Sihanouk reestablish his prior modus vivendi with the North Vietnamese?
If the latter happened, would North Vietnamese keep its distance from the Khmer Rouge and the latter movement would remain marginal, not on any real path to national takeover?
Even if so, and after the fall of Saigon in 1975, and the ouster of non-communists from the Laotian government in Vientiane in Laos in 1975, while Sihanouk could have a possible sense of satisfaction he survived by bending with prevailing Communist winds, complexity and "interesting times" would remain in Southeast Asia. Sihanouk's strategy of appeasing North Vietnam was above all based on the premise that China was the ascendant power in the region, and North Vietnam was aligned with China. How does that play later on in the 1970s when Chinese and Vietnamese relations become more oppositional, and Vietnam more aggressively courts the Soviet side of the Sino-Soviet dispute? Does Sihanouk's Cambodia tilt to the regionally and theoretically stronger China, or the nearby stronger united Vietnam?
* By the way, I see the abbreviation ITTL on this site a lot, what does that break down to? "In this time line?"
As of early 1970, Cambodian discontent with the heavy Vietnamese presence in the eastern portion of the country had built up to explosive levels, leading to mass demonstrations by urban and educated Cambodians.
While monarchical head of state Prince Sihanouk was on holiday, the government of his appointed Prime Minister, Lon Nol, supported and sponsored these demonstrations.
Per wiki:
The PoD is something happens between March 12th, and March 18th to prevent the next dramatic event that occurred in OTL:
As we can see, the conflict between Sihanouk on the one hand, and Prime Minister Lon Nol and Cambodian Assembly on the other hand escalated from zero to 60 MPH super-fast, became irrevocable, with Sihanouk and Lon Nol immediately condemning each other to death, and caused Sihanouk to do a complete 180 in his attitude toward the Khmer Rouge, who had killed members of his family previously.
The difference in this ATL* is Lon Nol, while still pushing his anti-North Vietnam agenda as far as he can take it, ultimately accepts Sihanouk is an indispensable figure, who can ruin everything if not brought on board. So, Lon Nol restrains his own anti-Sihanouk allies and sympathizers within the anti-Vietnamese movement in the National Assembly, and prevents them from meeting to hold a vote to oust Sihanouk. He also frantically messages Sihanouk to update him on the crisis and urge the necessity of him coming home to listen to the people's demands as the only way to calm things.
Based on news updates from Cambodia and frantic phonecalls from Lon Nol, reinforced by calls from royal relatives that Lon Nol encourages, Sihanouk speeds drastically speeds up his itinerary, making a brief office call with either Kosygin or Brezhnev or possibly even Soviet Foreign Minister to convey the message, "restrain the Vietnamese" and flying on to Beijing to do the same thing with Mao or Zhou Enlai or Lin Biao and then flying home.
When he arrives home I imagine he would try defuse tensions with the Vietnamese or certainly not order Cambodian forces to escalate things by trying to take material action to follow the departure ultimatum, but he will also be seeing the national fervor to stand-up the Vietnamese. He can mobilize peasant demonstrations in support of himself, and possibly dismiss Lon Nol, but it won't organically make the anti-Vietnamese frustration die-off.
So, what does Sihanouk do in terms of accommodating popular anti-Vietnamese sentiment vs. ignoring it? And pressuring the Vietnamese to reduce their footprint and visibility on Cambodian territory, vs. tolerating their presence. Reopening the port of Sihanoukville would be seen by the urban public as a very provocative move, at least if there is visibly Communist controlled and Communist helpful traffic emanating from there, so Sihanouk would be wise to leave that alone.
And what will the pattern of covert and overt US military activity, in the air, and potentially on the ground, over and in Cambodia be in 1970? Although in OTL, the overthrow of Sihanouk and Lon Nol's open anti-communist stand, and the outbreak of direct Cambodian - North Vietnamese fighting all strengthened pro-invasion of Cambodia arguments within the Nixon administration, according to Stanley Karnow, "[e]ven before the coup against Sihanouk, Nixon was inclined to invade Cambodia."
Would the US and ARVN do an invasion of Cambodia in 1970, or any time? Would Sihanouk come to fight the North Vietnamese, leading the latter to support the Khmer Rouge? Or would Sihanouk reestablish his prior modus vivendi with the North Vietnamese?
If the latter happened, would North Vietnamese keep its distance from the Khmer Rouge and the latter movement would remain marginal, not on any real path to national takeover?
Even if so, and after the fall of Saigon in 1975, and the ouster of non-communists from the Laotian government in Vientiane in Laos in 1975, while Sihanouk could have a possible sense of satisfaction he survived by bending with prevailing Communist winds, complexity and "interesting times" would remain in Southeast Asia. Sihanouk's strategy of appeasing North Vietnam was above all based on the premise that China was the ascendant power in the region, and North Vietnam was aligned with China. How does that play later on in the 1970s when Chinese and Vietnamese relations become more oppositional, and Vietnam more aggressively courts the Soviet side of the Sino-Soviet dispute? Does Sihanouk's Cambodia tilt to the regionally and theoretically stronger China, or the nearby stronger united Vietnam?
* By the way, I see the abbreviation ITTL on this site a lot, what does that break down to? "In this time line?"