Written By: Eliza Berman

On June 25, 1950, the Korean People’s Army of North Korea, with the backing of Joseph Stalin and against the backdrop of rising Cold War tensions, invaded South Korea. Two days later, having condemned the attack, the United Nations Security Council passed a resolution recommending military assistance to the Republic of Korea, as South Korea was officially known. By July, the U.S. was embroiled in a war that would last three years and cost more than a million lives in battle and hundreds of thousands more among civilians.

Less than a month after fighting began, LIFE published a series of photos by photographer Carl Mydans, who had documented the U.S. Army’s 1st Cavalry Division’s landing in P’ohang-dong on July 18. Mydans captured the unease of entering the unknown in a very literal sense, as members of the Division set sail from Japan without knowing their destination. Two weeks later, the Battle of P’ohang-dong would begin, lasting for 15 days and ending with a victory for the U.N. Forces.

As Mydans wrote to LIFE’s editors in the letter below, which accompanied his film, much of this war photography had to be reviewed and approved by the U.S. government before publication, as it might otherwise weaken the security of a nation at war.

Though the impact of the war is still extremely palpable in North and South Korea–where the demilitarized zone divides an economic power from an impoverished, disconnected country, the Korean War is often referred to as a forgotten war in U.S. history, sandwiched as it is between World War II and the Vietnam War. Many Americans even during wartime tuned out news from the front lines after realizing that the conflict wouldn’t likely escalate to the level of the recently concluded Second World War. Congress never issued a declaration of war, with President Harry S. Truman calling it a “police action.” It wasn’t until the late 1950s that Congress formally designated the conflict a war.

Photographs like Mydans’, and those made by his LIFE colleagues David Douglas Duncan, Margaret Bourke-White and Michael Rougier, ensure that the war can never truly be forgotten. Though Mydans’ early photos document the quiet days before battle, it’s impossible to look at them now without knowing the horrors that each of those men would face in short order.

Liz Ronk edited this gallery for LIFE.com. Follow her on Twitter @lizabethronk.

The 1st Cavalry in Korea, July 1950.

The first U.S. infantry outfit to shed blood in the Korean war was the 24th “Victory” Division, three of whose men are shown aboard a jeep in Korea. This image was on the cover of LIFE on July 31, 1950.

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

These soldiers of the 1st Cavalry left Japan for what was, to them, an unknown destination.

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

P’ohang-Dong’s harbor was dotted with landing craft to take men ashore. A scouting party had already reported there was no opposition. This was the fastest amphibious landing in history—planned and staged in 10 days.

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

These GI’s didn’t yet know what mission they were on.

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

General Hobart R. Gay and Rear Admiral J.H.Doyle, Korean War July 1950

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

Korean War July 1950

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

The 1st Cavalry in Korea, July 1950.

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

Korean War July 1950

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

Korean War July 1950

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

Korean War July 1950

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

Battle-dressed GIs boarded landing craft for a short ride to the beach at P’ohang-dong.

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

Korean War July 1950

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

Korean War July 1950

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

The 1st Cavalry in Korea, July 1950.

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

1st Cavalry GI’s on a jetty leading to a harbor beacon at P’ohang-Dong.

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

Jeeps being unloaded with help from Koresn people..

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

Newly arrived troops gathering at the beach and awaiting orders. Korean War July 1950

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

The 1st Cavalry in Korea, July 1950.

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

A GI standing by tank-busting 75-mm, recoilless rifles.

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

Korean War July 1950

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

Korean War July 1950

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

Korean War July 1950

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

Korean War July 1950

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

The 1st Cavalry in Korea, July 1950.

Carl Mydans The LIFE Picture Collection/Getty Images

The 1st Cavalry in Korea, July 1950.

Korean War July 1950

Carl Mydans The LIFE Picture Collection/Getty Images

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