Tensions between China and India over their Himalayan border have escalated, with China accused of moving thousands of troops into disputed territory and expanding a military airbase in the region. Thousands of Chinese People’s Liberation Army (PLA) troops are reported to have moved into sensitive areas along the eastern Ladakh border, setting up tents and stationing vehicles and heavy machinery in what India considers to be its territory. In response, the Indian army has moved several battalions from an infantry division usually based in the Ladakh city of Leh to “operational alert areas” along the border, and reinforcement troops have been brought in. The aggressive military posturing follows two skirmishes between the two sides on 5 and 9 May in the border areas of Pangong Lake and North Sikkim in Ladakh, in which more than 100 soldiers from both sides were injured. On Wednesday Donald Trump waded into the heightened standoff, claiming that he had “informed both India and China that the United States is ready, willing and able to mediate or arbitrate their now raging border dispute”. The high-altitude border has been aggressively contested and heavily militarised since 1962 when China launched an offensive into Indian territory, sparking a short but bloody war. Ashok K Kantha, a former Indian ambassador to China and now director of the Institute of Chinese Studies based in Delhi, said the recent incursions and border aggressions from China were “far from routine occurrences”. He said: “This escalation is serious; I don’t think this is just a localised incident. China’s behaviour is more aggressive this time, backed up by a fairly large number of troops, which is not typical of this border where troop levels tend to be low on both sides. It could be a territorial claim or part of a wider messaging to India that they need to be more mindful of China on sensitive geopolitical issues.” Kantha said it was “in the interest of both India and China to keep the situation under control and maintain relative peace”. China’s actions appear to be a response to India’s construction of roads and airstrips adjacent to the Line of Actual Control (LAC), which will improve connectivity and enable easier mobility for Indian troops in the area. Construction has paused during the coronavirus lockdown but is due to resume imminently. There have been diplomatic discussions as well as multiple meetings on a local level in an attempt to defuse the tensions. On Tuesday India’s prime minister, Narendra Modi, held a meeting with his national security adviser, Ajit Doval, plus his chief of defence staff and three security chiefs to discuss “bolstering India’s military preparedness to deal with external security challenges”. According to satellite footage published by the Indian news channel NDTV, there has been large-scale construction work at a Chinese military airbase less than 120 miles from the border in recent weeks, including the building of a new runway suitable for warplanes. “China is committed to safeguarding the security of its national territorial sovereignty, as well as safeguarding peace and stability in the China-India border areas,” a Chinese foreign ministry statement said. In a recent statement, India’s external affairs ministry blamed China for provoking the military escalation. “In fact, it is the Chinese side that has recently undertaken activity hindering India’s normal patrolling patterns,” the statement said. “The Indian side has always taken a very responsible approach towards border management.”