China is facing a monumental decision right now: whether to help Russia or not. On March 18, US President Joe Biden described to Chinese President Xi Jinping the “implications and consequences if China provides material support to Russia” at this time. To assist Russian President Vladimir Putin in dominating Ukraine might further China’s land-power interests, but it could also destroy China’s transition to one of the world’s newest sea powers , including becoming perhaps the most important member of the global economy. If Xi decides to back Putin, Western sanctions , tariffs and even a commercial blockade might be in China’s near-term future. This would derail Beijing’s hope for a 5.5 per cent growth rate this year. It could also disrupt critical oil and food supplies. China has long been considered one of the world’s greatest land, or continental, powers. The construction of the Great Wall is often cited as proof of China’s traditional focus on land power. Warfare was also constrained mainly to land warfare; Sun Tzu’s Art of War discussed how river currents could impact military strategy, but there is zero mention of warfare on oceans. After the Tiananmen Square crackdown , the fall of the Berlin Wall, and the 1991 demise of the Soviet Union, Sino-American relations became more strained. Russia quickly stepped in, selling China Sovremenny guided-missile destroyers and Kilo-class submarines. China even purchased the Ukrainian Soviet-era aircraft carrier Minsk and used it to reverse-engineer its own indigenous aircraft carrier. It also built warships based largely on Soviet-era technology. In recent years, China’s shift from being a land power to a sea power has speeded up: as of 2019, the People’s Liberation Army Navy is the largest in the world with over 300 ships, almost two dozen more than the US Navy, although the US ships tend to be larger and heavier, and the US fleet includes 11 nuclear-powered aircraft carriers. As a result of its modernisation efforts, China’s navy has become better equipped to meet its geographic responsibilities, especially in the Western Pacific. These include a complicated territorial dispute over the Senkaku/Diaoyu Islands with Japan, rising tensions over the Taiwan Strait , and disputed sovereignty over the South China Sea. China may have traditionally been a land power but, increasingly, fear of its aggressive maritime policy in the South China Sea and elsewhere has convinced many of its maritime neighbours, including New Zealand, South Korea and Vietnam, to increase cooperation with Japan, India, Australia and the United States (the so-called Quad ) as a counterweight to Beijing. Meanwhile, with the withdrawal of US forces from Afghanistan, and the possible knock-on effects of Western sanctions against Russia throughout Central Asia, there might soon be more military pressure on China’s western borders, forcing Beijing to shift away from the sea and return to being a land power. Ukraine crisis: why Afghanistan will be at the heart of new proxy wars From the heyday of the British Empire to the present, sea powers have set the global order and land powers have contested it. This dynamic clearly persists; Putin’s attack on Ukraine can be seen as the actions of a land power contesting the global order, and thus has been greeted with near-universal revulsion. Beijing must now decide whether to back Putin – the continental approach – or to become more deeply integrated into the maritime global order, which prizes free trade, freedom of navigation and respect for international law, through greater participation in multinational organisations seeking to uphold international legal norms. China’s shift to a “sea power” paradigm would significantly strengthen the global system and, in so doing, better position the rapidly growing list of countries favouring the positive-sum maritime approach to wait out a change of heart in Moscow. While the world’s attention is currently focused on Russia’s invasion of Ukraine, on the horizon it is still China that looms as potentially the most important, and the most dangerous, rising sea power during the upcoming “Pacific century”. Some commentators have even argued that war between the United States and China might be inevitable, but others disagree. A hundred years ago imperial Japan was in much the same position as China is today, and the world’s failure to introduce Japan peacefully into the international political order cost it dearly. Building a constructive and lasting political relationship with a fast-rising China is one of the most important security challenges facing the US today. Bruce Elleman is William V. Pratt Professor of International History at the US Naval War College, Newport, Rhode Island. The opinions expressed in this article are strictly his own, and do not necessarily reflect the views of the US government, US Navy, or US Naval War College