Two sides of the same ocean? America’s prospects vs China and Iran

The bottom line

> Chinese air and sea power pose formidable and direct threats to the US, while Iran remains a significant menace to Israel, potentially necessitating US intervention.

> Foreseeable conflicts against Iran and China are likely to require different types of forces, thus one war is unlikely to take American military capacity away from the other: US sea and air power could focus on the South East Asian theatre and US land power on the Middle East. The US would have the capacity to fight and win in both.

> It is impossible to predict the character of war, however, and many variables – such as the actions of Russia – could unexpectedly transform American fortunes.

Separated by the Indian Ocean are two of the US’s most immediate adversaries – China and Iran. Each threatens close allies of the US in a way that is already drawing in American military capacity. The election of Donald Trump increases the likelihood of direct conflict with both. However, the nature of the threats could not be more different; two wars on two fronts would be fought in different manners and with different resources. The US is likely to fare well – in the short term. There are, however, innumerable unknowns.

The Chinese threat

China should be considered the most concerning non-nuclear danger for the US. It has the will and the means to directly threaten US territories in the Pacific. It has also become increasingly aggressive towards neighbouring states, and US partners, in South East Asia as its leader, Xi Jinping, grows increasingly confident and outward-looking. Beijing is in grave danger of triggering a crisis that draws the US into war.

Chinese military exercises in the seas around Taiwan and incursions into the Taiwanese Air Defence Identification Zone, such as that in 2022 on former Speaker Nancy Pelosi’s visit to Taiwan, are the most salient causes for concern. Tensions continue to simmer in the South China Sea – where clashes with the Philippines Navy are becoming more violent – and on the Indian border – where disputes have boiled over into deadly brawls in recent years, despite occasional accords.

Growing antagonism is paired with growing capability. If deployed in tandem, China’s forces would severely restrict US freedom of operations in the Pacific and South China Sea.

At sea, in the air, and on land, China has put itself in a position to challenge the US. The People’s Liberation Army (PLA) Rocket Force has become a formidable conventional threat to US bases and maritime forces in the South China Sea and Pacific. The PLA Air Force is nearing parity with the US Air Force in numbers overall and certainly has superior numbers in-theatre given US commitments to Europe. The PLA Navy surpasses the US Navy in vessel numbers but remains inferior in tonnage and missile-launching capacity – for now. Forecasts suggest China will exceed the US in both within the decade, and it continues to develop the carrier strike capabilities it needs to confront the US Navy in fleet action.

That said, the US will be reassured by the problems that plague Chinese defence. Inefficiencies have been observed in the ability of the PLA’s branches to work together – the “jointness” at which the US excels. It is not clear how the Rocket Force would target US ships manoeuvring at sea without efficient cooperation with the Air Force or Navy; the PLA Air Force would face important logistical challenges in an extended conflict at distance from the mainland; and the PLA Navy has limited reach and experience beyond the First Island Chain that spans Japan, Taiwan, and the Philippines and much to learn about fleet operations.

As a result, China would aim to keep any war close to its shores. Moreover, the current economic slowdown in China could prompt defence cuts in the near future, as Beijing always prioritises spending on internal security.

The Iranian threat

The Iranian threat is very different. While Tehran is increasingly antagonistic, and armed with rockets and missiles, its most threatening capabilities are land-based, relying on proxy groups allied to the Islamic Revolutionary Guard Corps (IRGC).

Israeli actions have certainly damaged Iranian capabilities and capacity in recent months. However, the IRGC and Iranian conventional forces are extensive and resilient, and Tehran is set to triple the conventional defence budget over the next year. Even if Hezbollah has been crippled in Lebanon, powerful Iran-aligned groups are at play in Yemen, Iraq and Syria: it is a Syrian group that is suspected responsible for the January 2024 attack on an US outpost in Jordan – the first US service personnel killed by enemy action in the Middle East in years.

A wider conflagration that draws these groups into a concerted and coordinated campaign against Israel would require the US’s attention. While there are indications of Iranian restraint in the wake of the recent Israeli strike on Iran, there is a danger that should a weakened Iran feel cornered, it will lash out.

Washington – even with an unpredictable President Trump installed in the White House – will hope de-escalation is still on the table. Tehran has a ‘moderate’ president in Masoud Pezeshkian, and there have been signals that Ayatollah Khamenei is open to closer ties with the West. The IRGC may have lost some political capital with the Supreme Leader given its underwhelming performance against Israel – to the benefit of Tehran’s moderates.

There are also questions over whether IRGC-linked militias – which are likely to prioritise domestic interests – will toe Tehran’s line. Iran can use weapons deliveries as leverage, but these militias already have large stockpiles and can source more from Russia, North Korea, or even domestic production. Tehran will not want to cut off its allies completely while they act as Iran’s front line of deterrence.

American ability

Whether the US could simultaneously fight and win wars against both Chinese and Iranian threats is an exceedingly complex question. We can propose what the character of such wars would be, and thus how the US might fight them.

Against Iran, the US is likely to limit its involvement to supporting Israel as Iranian attention would largely fall on its regional adversary. The US already deploys missile defence systems and personnel in Israel to defend against Iran, which itself could be perceived as US involvement in war against Iran. Thus, what war with Iran means is unclear.

However, in the event of a conflict more serious than the current situation, US involvement would be focused on the ground theatre: the Israeli air force appears strong enough to face Iran alone, and the maritime theatre is unlikely to be decisive – an Iranian blockade of the Strait of Hormuz, for example, would hurt Iran more than the US and Israel. Deployment of additional ground-based air defence systems is foreseeable. If Iran-aligned groups attack Israel over land, US deployment of infantry is also imaginable: fatigued Israeli ground forces may struggle to resist a widespread offensive after over a year of war.

Any conflagration broader than this – a sprawling ground war across the Arabian Peninsula and into Iran, for example – is difficult to imagine, and unlikely to go far.

Against China, the US would devote far more resources out of necessity. The most probable war would involve a blockade of Taiwan or follow a crisis in the South China Sea, where the principal domains would be sea and air – not land. Indeed, a land war on the Korean Peninsula is far from Chinese interests and thus unlikely. The lessons of 1950 – where Communist Chinese support to North Korea precluded an invasion of Nationalist Taiwan – are fresh in the minds of the party elite.

A sea- and air-focused war would require the attention of much US sea and air power to face the fierce asymmetric threat posed by Chinese missiles while simultaneously resisting the symmetric threat posed by Chinese warships and aircraft operating close to home. In South-east Asia, unlike in the Middle East, the US lacks a partner than can do most of the heavy lifting against China. Though Japan, South Korea and Australia would be valuable contributors – partnerships such as AUKUS demonstrate their powerful shared will to counter China – they do not have the might to play a leading role. India, meanwhile, is likely to have its own interests, and European allies are unlikely to commit maximum resources to a war on the far side of the world – especially while action continues in Ukraine.

It is to the US’s advantage, however, that these two wars as envisioned are likely to centre on different domains. American planners would be able to commit maritime and air forces to one side of the Indian Ocean without sacrificing the war effort on the other. The US is therefore likely to have the capacity to fight and win in both theatres. However, wars are never fought as envisioned – the US will surely face unpredictability and find itself with impossible dilemmas to solve.

Russia, for example, would be a central concern for US leaders. Though analysis of the Russian variable is outside the scope of this piece, its military power remains globally relevant and may well be decisive. Simply the presence of Russia would tie down European forces and resources at home that might be of use to the US in the Middle or Far East; active Russian support for Iran or China would dramatically change calculations. Nuclear weapons, too, are not discussed in this piece – China’s growing nuclear capabilities under the PLA Rocket Force are extremely concerning.

The first part of defence, however, is deterrence. Here, much is already clear about how the US can fare on two fronts: poorly. US credibility and power to deter has suffered much in the Middle East.

In South-east Asia, American deterrence is far more robust but still flawed. One of few consistencies between recent and upcoming US administrations has been a hawkish policy towards China, and messaging is clearer around support for Taiwan – though Trump has conditioned his support on Taiwan spending more on its own defence.  The US backs this up with a powerful net of forces along the first and second island chains, a network of reliable allies in the region, and almost a century of experience in modern fleet operations and combined arms exercises with allied powers. Nevertheless, the US has been accused of idleness in the face of Chinese aggression in the South China Sea and Trump will be, once again, unpredictable and therefore undependable.

A question of wills

The prerequisite to this all, however, is whether the will exists to wage war on all sides. War is rarely desirable.

Little can be predicted about Trump’s approach, but US military leaders in Washington DC would focus on fighting China and be understandably unenthusiastic about a war on two fronts: China is a much more immediate threat, lying just across the Pacific, whereas Iran is on the far side of the world and the US is no longer reliant on the Persian Gulf for its energy needs.

Beijing, meanwhile, would prefer not to fight while Iran is at war: much of the imported oil that China relies on comes from Iranian wells. Tehran is even less likely to seek war: Iran is already reeling from conflict with Israel and has far more to lose than the US, Israel, or China. The American people, too, would veto deep involvement in another Middle Eastern war; however, they may support a brief, victorious war in South-east Asia, particularly if it is tied to Trump’s narrative of economic warfare against China for the benefit of the US economy.

Recent years have shown, however, that little can be predicted through rational calculation. Fate will have different ideas.

Image source: The U.S. National Archives