Chinese and Indian military reinforcements are building up along their disputed Himalayan border after soldiers there had their worst clash in decades last week. As tensions threaten to boil over, Indian Defence Minister Rajnath Singh used a visit to Moscow this week to urge Russia – the country’s biggest weapons supplier – to speed up delivery of its powerful S-400 Triumph air defence missile system, according to Indian media reports. Combined with India’s aircraft designed for high-altitude combat, the defence system could pose a threat to China’s military, according to observers. India was supposed to take delivery of the US$5.2 billion missile system by December 2021, but it has been delayed because of the coronavirus pandemic . Both China and India have the S-300 system – an earlier and inferior version of the S-400. But China already has the S-400 air defence system, with the last delivery in late 2018. Escalating tensions between China and India over the border dispute had spurred New Delhi to step up its air defences to match Beijing, according to Collin Koh, a research fellow from the S Rajaratnam School of International Studies at Singapore’s Nanyang Technological University. Moscow claims the S-400 is a cutting-edge air defence system that can detect and shoot down targets including ballistic missiles, enemy jets and drones up to 600km (373 miles) away, at altitudes of between 10 metres and 27km (33 feet and 17 miles). The border dispute between China and India last flared in 2017, when Indian and People’s Liberation Army troops had a two-month stand-off over Chinese road-building in Doklam, near a tri-junction border area that is claimed by both China and Bhutan, an ally of India. But last week’s confrontation in the Galwan Valley – part of the disputed Ladakh region in Kashmir – was the worst in decades, with at least 20 Indian soldiers killed and an undisclosed number of Chinese casualties, and it has raised fears of a further escalation of the conflict. How India and China’s deadliest clash in decades came about China has been expanding its arsenal on the border since the Doklam stand-off. That includes its J-20 stealth fighter jets, Z-20 helicopters, modified J-10C and J-11B fighter jets, Wing Loong II multi-role drones, Type 99A and Type 15 light tanks that can handle high altitudes and its Dongfeng missiles. Hong Kong-based military expert Liang Guoliang said although the S-400 might be able to detect and shoot down China’s J-10C and J-11B fighter jets, it would not be able to deal with the J-20 stealth fighters or other hypersonic weapons. “The S-400 is unable to knock down China’s DF-10 and Changjian-100 land-based cruise missiles, or the DF-17 road-mobile hypersonic ballistic missiles,” Liang said. “Its biggest contribution might be to protect the area near the capital New Delhi if a war breaks out.” China, India reinforcing border positions, satellite images show But Song Zhongping, another military commentator in Hong Kong, said if India also had the S-400, it would pose a threat to the PLA. “The S-400 system has a longer operating range and more accurate hit rate, and the India’s Russian Su-30 fighter jets and American Apache helicopters that are all designed for mountain and high-altitude battle shouldn’t be underestimated,” Song said. “Actually, the Indian military has a lot of mountain combat experience from skirmishes with Pakistan’s military over the years, but the PLA hasn’t engaged in battle for decades.” While India has tried to push the development of arms at home, more than half of its weapon systems are imported. The latest data on international arms transfers from the Stockholm International Peace Research Institute show that India accounted for 9.2 per cent of total global arms imports over the past four years, after Saudi Arabia – the largest importer at 12 per cent. China ranked fifth at about 4.3 per cent. Unlike India, almost all of the weapon systems the PLA has deployed in high-altitude areas have been developed in China. Comparing the military strength of the two countries, Koh in Singapore said it was difficult to assess based on weapons alone. “This comparison has to consider the human factor, doctrine and the ability of different armed services and branches to operate in an integrated fashion as well,” Koh said. “Based on this … I think it’s safe to say both the Indian and Chinese militaries have strengths to tout, and weaknesses they need to overcome when it comes to fighting a war along the Himalayan border.”