Gooooood question
Mike Collins said:
I thought this one was discussed before. Did a search and came up with nothing. If I missed it, sorry!
Its 1965-1966. GEN Westmoreland requests LBJ give him more troops and authorization to invade Laos. Pres. Johnson is impressed with the plan as he sees it as a quick way to stabilize the situation in Indochina so he can concentrate on his Great Society programs.
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While better than OTL's plan, he would be disappointed if he assumes it would cause quick results. In OTL he was concerned about this cross-border stuff provoking a stronger Chinese reaction. Maybe in this TL an earlier start to the Cultural Revolution makes it appear feasible? [In OTL he felt a little more secure increasing the bombing after that].
Even if not given extra troops, IMHO, Westmoreland should have argued that Laos should be the priority mission by late 1966 even if it meant canceling some other operations.
Mike Collins said:
A joint US/Thai/RVN force crosses international borders in early 1966 to seize Southern Laos as far North as the 17th parallel to cut off the Ho Chi Minh Trail. The Laotian government protests for good measure but not much as it sees the invasion as a way to bring long term stability (and the extra foreign aid/hush money is nice too!). The seized territory is made into a special administrative zone nominally under RVN control with promises to withdraw once "hostilities end". The US withdraws most of its invasion troops, but leaves the 1st CAV and 101st Airborne as a Quick Reaction Force.
USA's 1966 casualties will probably be a bit greater than OTL, but PAVN 1966 casualties will be much greater. As US forces extend to the Mekong, the PAVN will fight harder than historically, to keep its inflitration trails open. However, it will increasingly be getting damaged in big engagements with the US. In 1967, US casualties level off as the battelfield is shaped in a way more favorable to the US. Critical supplies and some VC reinforcements can still get through the US net, or even cross through Thai territory or the sea. However, the scale is much smaller than in OTL. It's a coin-toss whether Sihanoukville will see more communist traffic or if Sihanouk would resist the use of Sihanoukville by the commies in the firsr place.
There is extra international condemnation of the Laos incursion by western governments and liberal democrats, but the capture of so damn many PAVN on Laotian soil means the argument doesn't have legs in US domestic politics.
LBJ ends up with pretty much the same domestic political results he had in OTL 1966 and 1967. While the ATL war is going better than OTL, that timeline's inhabitants can't appreciate it, and Vietnam is by no means a popular war, even though Americans feel there is no alternative.
Viet Cong probably attempts Tet in 1967. It is crushed and the aftermath accelerates pacification in South Vietnam. The lack of major infiltration trails really starts to hurt the VC's ability to reconstitute in 1967 and 1968. However, during this time the PAVN continues to engage in massive Korean War style engagements with the US forces. The exchange ratio is even more lopsided against Hanoi than in OTL.
Johnson is not a popular man in any case though. He will face Eugene McCarthy's challenge but it might not get nearly as far as in OTL. LBJ is renominated. Nixon is the favorite to beat him in a two-man field, but Wallace is still likely to run and might split the conservative vote enough to give LBJ a shot. My logic for LBJ's unpopularity is that the majority of the public sullenly accepts US duty to fight, as in Korea, but they don't like it. After all, Truman probably wouldn't have been reelected during Korea.
There is a good chance of stabilizing the border by the mid-70s, after some years of heavy fighting continuing into 1971 or 1972. Vietnamization south of the 17th parallel helps the ARVN reconstruct the rural economy and build up its own forces better than OTL, though VC terrorists will exist at sme level throughout the 80s, and North Vietnam will be as menacing as North Korea.