India has deployed its Russian-made T-90 tanks against Chinese forces in the disputed border region of Ladakh.

But moving 45-ton tanks in a mountainous region with poor roads and bridges comes with its own challenges.

The Indian armor has been stationed at the desolate outpost of Daulet Beg Oldi, which lies at an altitude of 16,000 feet and features one of the world’s highest airfields. The outpost is a few miles from the Chinese border and just south of the strategic Karakoram pass, which India fears could be an invasion route for Chinese troops occupying the Aksai Chin area.

“With the Chinese People’s Liberation Army (PLA) deploying close to 50,000 troops in Aksai Chin, the Indian Army for the first time has deployed a squadron (12) T-90 missile firing tanks, armored personnel carriers (APCs) and a full troop brigade (4,000 men) at Daulat Beg Oldi to prevent any Chinese aggression from the Shaksgam-Karakoram pass axis, according to the Hindustan Times, citing top Indian military commanders.

While tempers appear to have cooled somewhat as Chinese and Indian troops disengage, both sides have sent in reinforcements. Significantly, China and India are sending tanks to the Himalayas, a vast mountain range that includes Mount Everest and a harsh climate arduous for both humans and vehicles.

China has deployed the Type 15 light tank, a 30-ton vehicle armed with a 105-millimeter cannon that can fire shells and anti-tank guided missiles. China claims that its 1000-horsepower diesel, coupled with the Type 15’s relatively light weight, will make the tank handy in mountainous terrain.

“With a powerful engine, the Type 15 lightweight main battle tank can effectively operate in plateau regions difficult for heavier tanks, and with its advanced fire control systems and 105-millimeter caliber armor-piercing main gun, it can outgun any other light armored vehicles at high elevations,” said China’s state-controlled Global Times.

Though lighter than the 70-ton U.S. M1A2 Abrams, Russia’s 45-ton T-90 main battle tank – essentially a modernized Cold War T-72  — is significantly heavier than the Type 15. Its 125-millimeter cannon can fire shells as well as AT-11 anti-tank guided missiles. Its defensive gear includes Kontakt-5 explosive armor and the Shtora infrared jamming system to stop incoming anti-tank rockets. While Chinese Type 15s have yet to see combat, Russian T-90s have fought in Syria, with at least one being badly damaged by a U.S.-made TOW anti-tank missile fired by Syrian rebels.

India has customized its variant, the T-90S Bhishma, with non-Russian gear such as a French thermal imaging system. The Type 15’s light weight may enable it to use roads and bridges that the T-90 can’t. One the other hand, India’s 1,000 T-90s have superior firepower and armor protection.

Arzan Tarapore, a non-resident fellow at the U.S.-based National Institute of Asian Research thinktank, believes the Indian T-90s are there as a warning to Beijing that Chinese territory is vulnerable to an Indian counteroffensive. “They are not there to defend Indian territory, but to threaten Chinese territory,” Tarapore tells me. “This is and has long been Indian doctrine: to threaten a punishing riposte against China – ideally to strengthen India’s hand in disengagement negotiations; or in the worst case, to actually try to seize Chinese territory as a bargaining chip to reverse China’s incursions.”

Chinese and Indian troops engaged in several mass fistfights in June in the disputed Galwan River valley, resulting in 20 Indian deaths and dozens of Chinese casualties.  Both nations fought in a brief war over Ladakh in 1962, in which China defeated poorly prepared Indian forces. Chinese now appears to be pushing against the demarcation line in response to India building a new highway to sustain its forces in the area.

This isn’t the first time that India has deployed tanks to Ladakh. During the 1962 war, India airlifted French-made AMX-13 light tanks aboard Soviet-made An-12 transport planes, and T-72s were sent in 2016.  In 1962, “the tank crews quickly acclimatized itself to the freezing temperature and ratified air at 15,000 feet,” noted one Indian news account. “The machines, however, faced more problems than the men. Low operating pressure and ratified air created problems in the cooling systems of the tanks and the freezing temperature affected the efficiency of their engines.”

Which raises the obvious question of how useful tanks will be in a mountainous area with very poor roads. During the Korean War, for example, U.S. tanks were invaluable during combat in the flatlands: once the fighting shifted to the mountains, American tanks became mobile howitzers, lobbing shells from inclined ramps at Communist troops in the hills.

And Ladakh itself is one of the most difficult places on Earth for tanks to operate. The thin air and temperatures in the region can plunge to 50 degrees below zero Fahrenheit, an Indian Army colonel told India’s NDTV in 2016. Indian tanks must use special fuel and lubricants at least twice every night, and the engines must be revved-up to keep the tank’s systems from freezing.

But even in the mountains, tanks still offer something unique: a big, heavily armored, mobile cannon that can deliver far more firepower than what a foot soldier can carry on his back. Modern vehicles like the T-90 also have thermal sights and other advanced sensors to spot targets at night and in fog. While there will be no armored blitzkriegs in the Himalayas, tanks can provide invaluable fire support to infantry. On the other hand, in restricted terrain, tanks will need the infantry to protect them from man-portable anti-tank rockets.

Should more clashes erupt in Ladahk, Type 15s may occasionally battle T-90s. But in the Himalaya mountains – nicknamed “the roof of the world” – the biggest danger to Chinese and Indian tanks isn’t the enemy. It’s the climate.

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