Inchon took place over 6 weeks before the first engagement with Chinese troops.
The Marines didn’t actually win but they survived and made it out - despite the best efforts of the Chinese army, Ned Almond and X Corp.
At that, I’ve never seen any documentary evidence that MacArthur was trying to start a nuclear war by killing off an American division - conversations in the men’s room of the Dai Ichi Building notwithstanding.
” In the X Corps area, the final elements of the ¡st Marine
Division and attached units arrive in the
Hamhung–Hungnam sector to conclude the breakout
from Hagaru. The ¡st Marine Division casualties, since
it departed Koto-ri on 8 December, amount to 51killed
(24 die of wounds), 16 missing and 256 wounded. The
1st Marine Division, upon its arrival at Hungnam, had
reversed the Chinese plans. The overwhelming forces
thrown into the region to surround the Marines and
annihilate the division failed. Instead, the ¡st Marine
Division fought its way along a sixty-mile route, and
through the support of air cover, devastated the Chinese
forces it encountered.
The fighting withdrawal of the 1st Marine Division,
which was at the time unaware that it had been written
off by many in the United States, evolves as the
greatest achievement of a trapped American fighting
force in the history of the United States. Between six and
eight Chinese divisions were planted to wipe out the
Marines and they failed, while sustaining overwhelming
casualties that greatly impeded their ability to
mount a full scale invasion against Hungnam. The Chinese
up to this point have not yet attempted to collapse
the perimeter, which is defended by contingents
of the U.S. 3rd Division and the U.S. 7th Division.
You are refering to the march from the Chosin Resivior.
Inchon was indeed a victory for the Marine Corps.