The US and China are picking sides in one of the world's most dangerous rivalries

• Relations between the US and India and between China and Pakistan are growing closer.
• India and Pakistan are looking to boost their military capabilities, while the US and China are looking for support of their regional and global ambitions.

In the final months of 2021, Pakistan commissioned the first of four Chinese-built Tughril-class frigates and confirmed its intentions to buy 25 of China's J-10C fighter jets.

Those are only the latest high-profile defense projects between Beijing and Islamabad, and they are emblematic of the growing relations between two countries with a common goal: countering the threat they see in India.

At the same time, India has increasingly turned to the US to meet its defense needs. The US has become a large supplier of arms to India over the past decade, and the two countries have deepened their defense cooperation as well.

The moves add another geopolitical layer to what was already one of the world's most intense rivalries.

Old rivals seek new friends

Before China became Pakistan's chief arms supplier in the 1990s, Islamabad relied on the US for higher-end defense equipment and assistance — a partnership borne out of cooperation to oust the Soviets from Afghanistan in the 1980s.

China and Pakistan's military relationship dates to the 1960s, but in recent years, the Pakistani military's hardware has increasingly come from China or through joint Pakistani-Chinese ventures.

Virtually all of Pakistan's main battle tanks are exported Chinese models or variants of Chinese tanks developed in Pakistan, like the Al-Zarrar. Pakistan has fielded upgraded variants of the Al-Khalid tank, developed jointly with a Chinese firm and in production since 2001, and begun acquiring Chinese-made VT-4 tanks.

The workhorse of Pakistan's Air Force is the JF-17, a fighter developed jointly with China and meant to replace Pakistan's aging Chinese-made J-7s. The PAF also operates a number of Chinese-made drones capable of strike missions.

As the PAF's use of its US-made F-16s is limited by the terms of their sale, buying J-10Cs may be an attempt to substitute or even replace the American fighter with one Pakistan can actually use against India.

At sea, three of the Pakistani navy's four Zulfiquar-class frigates were built in China like the Tughril-class frigates, the fourth of which was launched in December.

China is also helping Pakistan build eight Hangor-class submarines — a variant of China's Type 039A diesel-electric sub — splitting production between Chinese and Pakistani shipyards. They are expected to be delivered between 2022 and 2028 and will double the size of Pakistan's submarine fleet.

The defense relationship goes beyond weapons sales. China and Pakistan regularly conduct joint and multinational military exercises. Officials from both countries speak of their relationship in glowing terms, describing it as "close as lips and teeth" and "sweeter than honey."

As its two fiercest rivals have deepened their defense ties, India has deepened its own military partnerships, in particular with Russia, which has for decades supplied India with advanced hardware.

The US has historically been reluctant to sell arms to India because of New Delhi's ties with Moscow and fears that those weapons may be used in a war in South Asia. But in recent years India has increased its purchases of defense equipment from the US and other Western countries.

Since the signing of the New Framework for the US-India Defense Relationship in 2005, India has purchased dozens of US-made cargo aircraft and attack and transport helicopters — including MH-60R Seahawk and P-8I maritime patrol planes, both of which are important for Indian efforts to keep an eye on increasing Chinese activity in the Indian Ocean.

The F/A-18, the F-15EX, and the F-21 (an F-16 variant made just for India by Lockheed Martin) are all in the running to fill an Indian order for 114 new fighter jets. The F/A-18 is also a contender to be used aboard India's first domestically built aircraft carrier, INS Vikrant.

The US has also sold India lethal weaponry such as torpedos, anti-ship missiles, naval guns, an anti-aircraft system, M777 howitzers, and 144,000 US-made SIG716 rifles.

India's military participates in land and naval exercises with the US, and the two sides have expanded their intelligence-sharing amid tensions along India's disputed border with China.

Geopolitical realities

The developments in the China-Pakistan and US-India relationships reflect the geopolitical realities in South Asia and across the Asia-Pacific region.

India and Pakistan have looked to the US and to China to boost their military capabilities, while the US and China are looking to India and Pakistan to support their regional and global ambitions.

Pakistan's reliance on China, in particular Chinese investment in the China-Pakistan Economic Corridor, will only increase in the aftermath of the US withdrawal from Afghanistan. The withdrawal is also likely to reduce the US's commitment to Pakistan, as they are aligned on few other issues.

"The China-Pakistan relationship is deeper because China's goals are more aligned with what Pakistan wants, which is the ability to counter its main rival, India," Timothy Heath, a senior international and defense researcher at the Rand Corporation think tank, told Insider.

"China hopes to keep a strong, relatively well-equipped and well-armed Pakistan as a partner, because from Beijing's perspective, that helps keep a potential rival — namely India — distracted and unable to cause more problems for China," Heath added.

Some in Pakistan are wary of going all-in on China and may seek rapprochement with the US, particularly if China grows reluctant to invest further in Pakistan's struggling economy. Beijing has also stopped short of making a military commitment to Pakistan — largely because it fears getting dragged into a full-blown conflict between Pakistan and India.

"They have a good deal where they use Pakistan to box in India and they stay outside and allow those two to bleed each other and beat each other up a little bit," Heath said.

While Beijing wants to avoid "extreme escalations," Heath said, "tensions of a low simmering type are useful for China."

For India, the US has emerged as a prime partner as Delhi grows more concerned with Chinese ambitions and the potential for conflict along its borders with both China and Pakistan.

The US-India relationship is "primarily driven by a strategic convergence," said Rahul Bhatia, a research analyst at Carnegie India.

"New Delhi and Washington essentially want multipolarity in the Indo-Pacific and a rules-based international order, which very loosely translates to containing China," Bhatia said, adding that "they need each other for that."

But despite a deepening defense relationship, India doesn't seek a full-fledged alliance with the US for a variety of political and economic reasons.

"When the US wants to sell a country arms, they are looking at building up a strategic partnership and interoperability. What India looks at when it's buying arms is building its own defense industrial base and the transfer of technology," Bhatia said.

Moreover, India does not want to break from its traditional stance of non-alignment.

"They want to maintain their strategic autonomy," Heath said. "That's a very deeply rooted tradition vigorously alive in India today."