Vance wants the US military to focus on China over Russia. There's one big problem with that plan.

• Donald Trump on Monday selected Ohio Sen. JD Vance as his 2024 running mate.
• Vance has suggested the US should focus on the threat presented by China, rather than Russia.
• But Russia and China are working together against the US, say analysts.

Donald Trump unveiled his vice president pick and likely political heir, Ohio Sen. JD Vance , to a rapturous welcome at the RNC conference in Milwaukee this week.

But in European capitals, Trump's selection of Vance was greeted with deepening concern.

Vance, like Trump, has long cast doubt on the necessity of the US commitment to NATO, which for decades has been the main bulwark against Russian aggression in Europe.

He has also questioned US support for Ukraine in its battle against the Russian invasion.

A US withdrawal from NATO could pave the way for a Russian victory in Ukraine and, European leaders fear, an attack on NATO itself.

Instead, Vance, in common with other so-called "Asia First" Republicans, wants the US to instead focus on what he views as a far greater challenge to US security: China.

In a Monday interview with Fox News, Vance called China the "biggest threat" to the US, adding that Ukraine was a distraction.

Vance claims that the US needs to counter China's economic might, and has backed an increase in tariffs on China that he claims would help boost US industry.

Supporters of refocusing on the China threat believe that the US needs to pick its battles carefully. They believe Ukraine is draining resources the US might need in a confrontation with China, which has the world's largest military.

"China's rapid military build-up has changed the calculus, especially for the 'Asia First' crowd, who see US allies in Europe as more than capable of carrying a heavier burden when it comes to their own defense," said Graeme Thompson, an analyst with the Eurasia Group.

But there's a major problem with that view, say analysts.

China and Russia are working together

Focus solely on the threat posed by Beijing ignores the extent to which China and Russia are interlinked.

"Retrenchment in the face of Russian aggression in Europe would undermine US strategic competition with China in the Indo-Pacific, not enhance it," wrote Michael Green, an analyst at the Center for Strategic and International Studies, and Gabriel Scheinmann, the executive director of the Alexander Hamilton Society, in an article in Foreign Policy in the wake of the 2022 Russian invasion.

Far from being isolated threats that the US can separate and prioritize, Russia and China are, in fact, working closely together to topple US global power.

China has provided Russia with diplomatic, economic, and military support in the form of dual-use goods for its war in Ukraine.

In the past month alone, China has held joint military exercises with Belarus, a Russian ally, on NATO's border, and the Chinese and Russian navies have engaged in joint naval exercises.

"Though one could certainly articulate putting a region first in terms of resources and effort, ignoring one of the threats altogether makes little strategic sense," Paul Cormarie, an analyst at the RAND Corporation, told Business Insider, pointing to the close cooperation between the authoritarian powers.

Experts, such as Hal Brands at Johns Hopkins University, believe that China is watching the Ukraine war carefully for signs of Western weakness and will likely launch a campaign to seize control of Taiwan if Russia is victorious.

According to critics of Vance's position, by allowing Russia to seize territory and build its military power in Europe, the US would be helping embolden China's aggression.

It's a threat that US allies in East Asia understand clearly, with Japan having provided Ukraine with billions in aid, knowing that a defeat for the European country directly increases the threat it faces from China. Taiwan and South Korea have also provided Ukraine with support.

Will Trump and Vance follow through?

It remains to be seen whether, if elected, Trump and Vance will follow through on their rhetoric, reduce US NATO support, and compel Europe to pay for its own security.

Despite his incendiary claims on the 2016 campaign trail, Trump, while in office, continued to support NATO. Vance himself has said that US allies in Europe should not be entirely abandoned but simply placed lower on the list of US security priorities.

But this time, observers say, Trump likely won't be retrained by figures such as HR McMaster or James Mattis, officials in his administration who acted as "guardrails" diverting the president from acting on rash impulses.

Instead, he'll likely be surrounded by figures such as Vance, who back his hardline brand of nationalism and narrow focus on China.

Indeed, Trump's former national security advisor, John Bolton, believes that Trump would almost certainly seek to withdraw the US from NATO if elected.

A second Trump term could lead to celebrations not just in Moscow, but in Beijing if Trump and Vance act on their declared hostility to NATO and US support for Ukraine.