Let’s Learn About North Korea – Part 3 – June 25, 1950: The Outbreak of the Korean War (Part 1)

Yes, we have finally reached the main story.

June 25, 1950
Hereafter, the Korean War
The Outbreak of the Korean War

North Korean forces began shelling South Korean positions along the 38th parallel, marking the beginning of the Korean War.

As I explained earlier, the 38th parallel was established when the United States and the Soviet Union divided the Korean Peninsula into northern and southern zones to administer and support after its liberation from Japan.

Although it was initially intended as a temporary dividing line, it eventually became the boundary separating North and South Korea.

Across that line,
approximately 89,000 North Korean troops advanced southward,

supported by around 200 Soviet-made T-34 tanks and

approximately 120 aircraft, including Soviet-made Yak-9 and Yak-7 fighters, Il-10 ground-attack aircraft, and Po-2 training and reconnaissance aircraft.

Excluding the weapons supplied by the Soviet Union, the military capabilities of North and South Korea might have appeared relatively similar at the time.

In that sense, it is reasonable to say that the Soviet Union was effectively involved from the very beginning of the war.


In my personal opinion,

this was more than simple intervention or military assistance.

Without the overwhelming military advantage provided by those tanks and aircraft,
North Korea might not even have been able to launch the war in the first place.

I believe Soviet support was therefore an essential factor.

So, what was the situation in the South on June 25?

There was practically nothing.

By the end of June 1949, the US occupation forces had essentially withdrawn from South Korea.

Only a US military advisory group of approximately 500 personnel remained to assist with the organization and training of the South Korean military.

Forget fighter aircraft.
South Korea did not have a single tank.

In other words, South Korean troops were essentially expected to stop tanks and aircraft with nothing more than rifles in their hands.

Under those circumstances, the initial offensive, supported by tanks and aircraft, was

almost like facing a nuclear weapon in terms of the overwhelming asymmetry in military power, wasn’t it?

As a result, Seoul fell in just three days.

South Korean forces were forced to retreat farther and farther south, repeatedly attempting to establish defensive positions before withdrawing again.

– Timeline of US and UN Forces During the Korean War –

United Nations Security Council Resolutions

June 25, 1950 — Resolution 82: Condemned North Korea’s armed attack and called for the withdrawal of North Korean forces to the north of the 38th parallel.
June 27, 1950 — Resolution 83: Recommended that UN member states provide assistance to the Republic of Korea.
July 7, 1950 — Resolution 84: Established a unified command under US leadership for the UN forces.

British forces began joining the fighting in earnest around August 29, when approximately 1,578 personnel from the British 27th Infantry Brigade arrived.

The Royal Australian Air Force began combat missions on July 2.
Flying P-51 Mustang fighters from Iwakuni Air Base in Japan, Australian aircraft attempted to disrupt North Korean supply lines on July 3.

Deployment of US Ground Forces

July 1, 1950 — Task Force Smith, belonging to the US 24th Infantry Division stationed in Japan, arrived in Busan.

These are generally regarded as the first US ground combat troops deployed to Korea.

July 5, 1950 — Battle of Osan, Jukmiryeong
The force consisted of approximately 540 soldiers, primarily from two infantry companies, supported by six 105 mm howitzers.

VS

Approximately 5,000 North Korean troops and 34 tanks.

The difference in troop numbers was unbelievable, wasn’t it?

Yet they managed to hold out for six hours,

buying valuable time for follow-up forces to establish defensive positions.

From that point onward, the United States continued deploying additional troops while conducting delaying actions and retreating southward.

Major Battles After Osan: A Timeline

Date	Major Battle Area	What Happened
July 5	Osan, Jukmiryeong	Task Force Smith engaged North Korean forces before withdrawing.
July 8–12	Jochiwon	US forces attempted to delay the North Korean advance.
July 13–16	Geum River Defensive Line	US forces fought defensive battles along the Geum River before retreating.
July 19–20	Daejeon	The US 24th Infantry Division and other forces defended the city, but North Korean troops eventually captured it.
Late July	Yeongdong and Sangju areas	US and South Korean forces continued fighting defensive actions while retreating.
Late July–Early August	Jinju and Masan areas	Fighting aimed to stop the North Korean advance through southwestern Korea.
Early August	Nakdong River Defensive Line	South Korean and US forces established the Busan Perimeter and concentrated on defending it.
August–Mid-September	Dabudong, Daegu, Masan, and Pohang	Allied forces repelled North Korean attempts to break through the Busan Perimeter.

The table above shows the major battles.

If we roughly map the overall retreat toward Busan, the movement looked like this.

That is how the situation unfolded.

Looking at the retreat toward Busan, there is not a single arrow pointing northward in the opposite direction.

Of course, there were battles in which South Korean and UN forces advanced northward and achieved victories, but these did not significantly change the overall course of the retreat.

Why were they forced onto the defensive even after the United States began helping?

The reason was that the speed of their defeats and retreats exceeded the speed at which US and UN reinforcements could arrive.

As I mentioned earlier, South Korean forces had little more than rifles, while tens of thousands of North Korean troops launched a surprise attack supported by tanks and aircraft.

In the early stages, American reinforcements were also arriving in relatively small groups, sometimes numbering only 500 or 1,000 soldiers.

They were not arriving in tanks or jet fighters, either.

All they could do was conduct delaying actions and hold out until the main forces arrived.

Fortunately, the first major contingent of approximately 13,059 troops from the US 25th Infantry Division began arriving in Busan

between July 10 and 15, 1950.

This helped the defenders hold their ground.

By slowing the enemy’s advance, these troops helped create the conditions for a future counteroffensive.

Afterward,

US forces bypassed the main combat zone

and advanced all the way to Yecheon, where they achieved a victory.
However, under continued pressure from the advancing North Korean forces,

they had no choice but to turn back toward the rear.

As you can see, US forces won the Battle of Yecheon on July 20, but subsequently changed direction and arrived in Masan on August 3.

After that,

one of the fiercest battlefronts of the war, the Nakdong River Defensive Line, became the scene of approximately six weeks of intense fighting.

And finally,

under the command of General Douglas MacArthur,

September 15, 1950 — The Incheon Landing Operation

The operation began.

North Korean forces had come within a single step of painting the entire peninsula red.

Then, they were hit with a devastating counterattack.

General MacArthur launched the Incheon Landing Operation,

cutting off North Korean supply lines—in other words, striking directly at their rear.

These forces

sailed by ship from Kobe, Japan, and Busan, South Korea, taking different routes before landing at Incheon.

Kobe, Japan → Incheon: The US 1st Marine Division departed on September 11 and landed on September 15, taking approximately four days.

Busan → Incheon: The US 5th Marine Regiment departed Busan on September 12 and landed on September 15, taking approximately three days.

Those must have been an incredibly long three or four days.

From the initial landings on September 15,

By the night of September 16: Approximately 15,000 troops and 1,500 vehicles had landed.

September 18: The originally scheduled initial landing force and its vehicles had completed landing.

By September 21,
an additional 53,882 troops, 6,629 vehicles, and 25,512 tons of cargo had been unloaded.

Following the landing operation,
the counteroffensive also began at the Busan Perimeter.

South Korean and UN forces pushed northward, driving North Korean troops back. On September 26, near Osan,

they linked up with troops from the US 7th Infantry Division, which had landed at Incheon.
This was known as the Rendezvous at Osan.

After that,

Seoul was recaptured on September 28.

In early October, UN forces crossed the 38th parallel and advanced northward.

The Korean War was about to enter a completely different phase.

If the advance continued any farther,

American forces would soon be positioned right on the doorstep of China and the Soviet Union.

Yes, China and the Soviet Union were about to make their moves.