In the summer of 1950, North Korea attacked South Korea, and the 1st Cavalry Division was rushed to Korea to help shore up the Pusan Perimeter. After the X Corps attack at Inchon, a breakout operation was launched at the Pusan Perimeter. The 1st Cavalry Division remained in the line until it was relieved by the 45th Infantry Division from the United Statesicon Army National Guard in January 1952. Following the relief, the division returned to Japanicon. 1957 saw the division back in Korea, where it remained until 1965.

During the Korean War, there were disparaging rumors about the 1st Cavalry Division's fighting abilities, including a folk song of the time called "The Bug-Out Ballad".[4] It was also rumored that the series of engagements that gave rise to the song were due (at least partly) of the myth that the Division lost its unit colors[5]. Other Army and Marine units disparagingly described the division shoulder insignia as representing 'The horse they never rode, the river they never crossed, and the yellow speaks for itself'. Another version goes: "The shield they never used, the line they never held, the horse they never rode, and the yellow speaks for itself." The incident that apparently gave rise to this false rumor appears to be the Unsan Engagement which took place on 1 and 2 November 1950 at Unsan, Korea. In that battle, the 8th Cavalry, a component of the 1st Cavalry Division, was pushed back from positions in and around the town of Unsan by vastly superior Chinese forces. The regiment was severely battered, suffering heavy casualties and losing a considerable amount of equipment. This was one of the first major Chinese operations in the Korean War and, like the Changjin (Chosin) Reservoir Battle of this same period, it took the United Nations Command by surprise. Considering the circumstances, the 8th Cavalry fought very well, and it has never been criticized for its conduct in this operation

The Bug-Out Ballad (Moving on)

Hear the patter of running feet
It's the old First Cav in full retreat
They're moving on; they'll soon be gone
They're haulin' a$$, not savin' gas
They'll soon be gone.

Over on that hill there's a Russianicon tank
A million Chinks are on my flank
I'm movin' on, I'll soon be gone
With my M-1 broke, it ain't no joke
I'll soon be gone.

Million Chinks comin' through the pass
Playin' burp-gun boogie all over my a$$
I'm movin' on, I'll soon be gone
With my M-1 broke, it ain't no joke
I'll soon be gone.

Twenty thousand Chinks comin' through the pass
I'm tellin' you, baby, I'm haulin' a$$
I'm moving on; I'll soon be gone
I'm haulin' a$$, not savin' gas
I'll soon be gone.

Standin' in a rice paddy up to my belly
From then on, they called me "Smelly"
I'm moving on; I'll soon be gone
I'm haulin' ***, not savin' gas
I'll soon be gone.

Here's papa-san comin' down the track
Old A-frame strapped to his back
He's moving on; he'll soon be gone
he's haulin' ***, not savin' gas
He'll soon be gone.

Here's mama-san comin' down the track
Titty hangin' out, baby on her back
She's moving on; she'll soon be gone
From her tits to her toes, she's damn near froze
She'll soon be gone.

I sung this song for the very last time
Gonna get Korea off my mind
I'm moving on; I'll soon be gone
I done my time in the **** and slime
I'm movin' on.

From Ther Erotic Muse, Cray
Collected from Cray, 1953
Note: a parody of a country classic by Hank Snow

In Vietnam, they sang:
The McNamara Line is a hundred miles long
Completely surrounded by Viet Cong
I'm movin' on etc.