Twenty Indian soldiers were killed by Chinese troops late Monday in a clash along the disputed India-China border, the first such episode in decades, military experts said. The violence is a continuation of a decades-old dispute between the two nuclear powers over the precise location of their Himalayan border.

What is the ‘Line of Actual Control’ and why does it matter?

Six decades ago, India and China went to war over a border dispute that ended with an uneasy truce in 1962.

While no border has ever officially been negotiated along the forbidding stretch of land high in the Himalayas that divides the two nations, the truce established a 2,100-mile-long Line of Actual Control.

Since then, an uneasy peace has held. But every time there is a flare-up of violence, the world watches anxiously.

China and India are the two most populous nations on earth, both armed with nuclear weapons, led by governments that have built support, in large part, by appeals to nationalist sentiment.

In recent months, tensions have spilled over into brawls between soldiers. And late Monday, the violence reached dangerous heights when the 20 soldiers, including an army officer, were killed by Chinese troops.

It was said to be the first time in decades that the fighting at 14,000 feet had led to casualties.

What Is the 'Line of Actual Control' Border Between India and China? 1

Line of Actual

Control

CHINA

PAKISTAN

Diamer Bhasha dam

CHINA

NEPAL

GILGIT-

BALTISTAN

Controlled by Pakistan

Area of detail

Disputed borders

or ceasefire lines

CHINA

INDIA

Galwan Valley

JAMMU

AND KASHMIR

Controlled by India

Bay of

Bengal

Pangong Tso

Arabian

Sea

CHINA

CHINA

PAKISTAN

Lipulekh

Pass

INDIA

Naku La

NEPAL

BHUTAN

100 miles

BANGLADESH

What Is the 'Line of Actual Control' Border Between India and China? 2

Line of Actual

Control

Diamer Bhasha dam

CHINA

CHINA

PAKISTAN

GILGIT-

BALTISTAN

Controlled by Pakistan

NEPAL

Disputed borders

or ceasefire lines

CHINA

Area of detail

Galwan Valley

JAMMU

AND KASHMIR

Controlled by India

INDIA

Pangong Tso

CHINA

Bay of

Bengal

CHINA

Arabian

Sea

PAKISTAN

Lipulekh

Pass

INDIA

Naku La

NEPAL

BHUTAN

100 miles

BANGLADESH

What Is the 'Line of Actual Control' Border Between India and China? 3

Line of Actual

Control

Diamer

Bhasha dam

CHINA

CHINA

GILGIT-

BALTISTAN

Controlled by Pakistan

PAKISTAN

Disputed borders

or ceasefire lines

NEPAL

CHINA

Area of detail

Galwan Valley

JAMMU

AND KASHMIR

Controlled by India

INDIA

Pangong Tso

Bay of

Bengal

CHINA

CHINA

Arabian

Sea

PAKISTAN

Lipulekh

Pass

INDIA

Naku La

NEPAL

100 miles

What Is the 'Line of Actual Control' Border Between India and China? 4

Line of Actual

Control

CHINA

CHINA

GILGIT-

BALTISTAN

Controlled by Pakistan

1

Disputed borders

or ceasefire lines

Area of detail

CHINA

2

INDIA

JAMMU

AND KASHMIR

Controlled by India

3

Bay of

Bengal

Arabian

Sea

CHINA

CHINA

PAKISTAN

4

INDIA

5

NEPAL

100 miles

1

2

3

4

5

Diamer Bhasha dam

Galwan Valley

Pangong Tso

Lipulekh Pass

Naku La

What Is the 'Line of Actual Control' Border Between India and China? 5

CHINA

Disputed borders

or ceasefire lines

1

Ctrl. by Pakistan

CHINA

2

Ctrl. by India

3

CHINA

CHINA

PAKISTAN

4

INDIA

NEPAL

5

100 miles

1

2

3

4

5

Diamer Bhasha dam

Galwan Valley

Pangong Tso

Lipulekh Pass

Naku La

CHINA

PAKISTAN

NEPAL

Area of detail

INDIA

Bay of

Bengal

Arabian

Sea

Source: Satellite image via Microsoft Corporation Earthstar Geographics

By Jugal K. Patel

What are they fighting over?

While the Line of Actual Control was devised to create a demarcation line and to ease tensions between the nations after the 1962 war, many areas remain in dispute.

Both China and India have pressed their claims by building up infrastructure like roads, telephone lines and airstrips, and by sending troops on regular patrols.

The demarcation line runs through a territory known as Ladakh. It is part of Kashmir but located in the region’s lesser-known Buddhist region.

Ladakh borders Tibet and is even sometimes referred to as Little Tibet. Sitting at the crossroads of several important trade routes, the territory has a rich history of commerce. But that came to an end when China closed the borders with Tibet and Central Asia in the 1960s.

Now, the sparsely populated but stunningly beautiful land is mostly known as a tourist destination.

What led to the current standoff?

In May, an enormous brawl broke out between Chinese and Indian soldiers stationed at camps high in the Himalayas.

Beijing’s reaction was swift and forceful.

Chinese troops confronted Indian soldiers at several other remote border points in the mountains, some more than 1,000 miles apart. Since then, both armies have rushed in thousands of reinforcements. Indian analysts say that China has beefed up its forces with dump trucks, excavators, troop carriers, artillery and armored vehicles and that China is now occupying Indian territory.

And as the world has been distracted by the coronavirus pandemic, Beijing has taken a series of aggressive actions in recent weeks to flex its economic, diplomatic and military muscle.

For India, the Chinese incursions and maneuvers at multiple points along the demarcation line have raised suspicions of a concerted campaign to exert pressure on the government of Prime Minister Narendra Modi.

The spark for the recent tensions seems to have been a road to a remote air force base that the Indian Army is building through mountain passes in the Galwan Valley, which military analysts say is fully within Indian territory. Experts say that the Chinese are determined to frustrate India’s efforts to upgrade its military positions.

Preliminary reports on Tuesday indicated that the Indian soldiers had not been shot, but had been killed in a fight involving rocks and wooden clubs.

It was not immediately clear how India would respond.