Relations between India and China have been worsening in recent months. The two world powers are facing off against each other along their disputed border in the Himalayan region.
In 400 words, here's some background to help you understand what's going on.
What's the source of tension?
The root cause is an ill-defined, 3,440km (2,100-mile)-long disputed border.
Rivers, lakes and snowcaps along the frontier mean the line can shift, bringing soldiers face to face at many points, sparking a confrontation.
The two nations are also competing to build infrastructure along the border, which is also known as the Line of Actual Control. India's construction of a new road to a high-altitude air base is seen as one of the main triggers for a clash with Chinese troops in June that left at least 20 Indian soldiers dead.
How bad is the situation?
Despite several military-level talks, tensions continue.
The most recent skirmish - on 20 January - left troops on both sides injured. It took place along the border in India's Sikkim state, which is sandwiched between Bhutan and Nepal.
The year 2020 was particularly violent. The June clash in the Galwan Valley - fought with sticks and clubs, not guns - was the first fatal confrontation between the two sides since 1975.
India acknowledged its deaths. China did not comment on reports it also suffered fatalities.
In August, India accused China of provoking military tensions at the border twice within a week. China denied both charges and blamed India for the stand-off.
In September, China accused India of firing shots at its troops. India accused China of firing into the air.
If true, it would be the first time in 45 years that shots were fired at the border. A 1996 agreement prohibited the use of guns and explosives near the border.
What's the bigger picture?
The two countries have fought only one war, in 1962, when India suffered a humiliating defeat.
But simmering tensions involve the risk of escalation - and that can be devastating given both sides are established nuclear powers. There would also be an economic fallout as China is one of India's biggest trading partners.
The military stand-off is mirrored by growing political tension, which has strained ties between Indian Prime Minister Narendra Modi and Chinese President Xi Jinping.
Observers say talks are the only way forward because both countries have much to lose.