Ninety years ago, on 18 September 1931, a junior Japanese military officer detonated an explosive that had been carefully laid by a Japanese-owned railroad near the northeastern Chinese city of Shenyang (then known in the West as Mukden). The blast did little damage, but that wasn’t the point. The Japanese blamed Chinese soldiers for the explosion, which they used as a pretext to capture Shenyang and occupy the entire territory, known as Manchuria.

Though Manchuria was a Chinese territory, controlled by warlords loyal (in name if not in reality) to China’s nationalist government, thousands of Japanese soldiers were stationed there under the terms of an earlier treaty. This enabled Japanese forces to overrun the area quickly. Within weeks of the Manchurian Incident, they controlled the southern part of Manchuria, with the north following by early 1932.

This was no imperial invasion, the Japanese claimed. Rather, it was a response to the cries for help coming from the people of Manchuria, who were suffering under the warlords’ iron-fisted rule. Japan merely wanted to help oppressed people to establish an independent state that would liberate them from the maelstrom of corruption that enveloped the rest of China.

Japan even had a name for this new state: Manchukuo, or ‘land of the Manchus’. To add lustre to their vision, they recruited the most famous Manchu around—China’s last emperor, Puyi—to lead it. (Having been deposed in 1912, Puyi was available for alternative monarchical engagements.)

The effort to create an independent Manchurian state became an international cause célèbre, and a test for the League of Nations, the precursor to the United Nations tasked with preserving peace after World War I. The League sent a commission, led by British diplomat Lord Lytton, to investigate the situation. The commission concluded that Japan had effectively staged a coup.

Japan was undeterred. It withdrew from the League of Nations, and held onto its Manchurian puppet state until its defeat in World War II. At that point, the Soviet Union took over, occupying the territory for a year.

At the same time, however, the long-running war between the Chinese Nationalists and Communists was heating up again, with Mao Zedong’s forces claiming more and more territory, beginning in the northeast. By the time the Communists established the People’s Republic of China in 1949, the Manchurian provinces were firmly within their grasp.

But the Chinese have not forgotten the 14-year occupation of Manchuria. In fact, official Chinese doctrine establishes the 1931 Manchurian Incident as the beginning of World War II. And every year on 18 September sirens wail in Shenyang and other cities in the region to commemorate not just the explosion itself but the atrocities that followed. These include the horrific experiments that Unit 731—the Japanese army’s research-and-development unit for biological and chemical warfare—carried out on live subjects.

What do these memories mean today? Within China, the message is clear: before the People’s Republic was established, the country was weak and vulnerable to foreign invasion. A major museum in Shenyang, which tells the story of those who died fighting the Japanese occupation, reinforces the narrative that China’s Nationalist leaders did little to protect the country from humiliation by invaders.

But while China’s leaders are eager to use the Manchurian Incident to advance their favoured narrative of the past, they hesitate to acknowledge echoes of the event in the present, particularly when it comes to the actions of China’s close military and strategic partner, Russia. In 2008, when Russia invaded Georgia, Chinese leaders, perhaps quietly seething over the distraction from the start of that year’s Olympic Games in Beijing, refrained from voicing strong support for its actions (unlike other Kremlin allies such as Belarus). But they didn’t push back either, merely calling for all sides to remain calm.

Likewise, in 2014, China refused to denounce Russia’s occupation and annexation of Crimea from Ukraine, or the Kremlin-organised plebiscite, unmonitored by any neutral body, that endorsed it. When the UN Security Council considered a resolution condemning the referendum, China abstained.

Of course, China itself has been known to redefine territorial questions to its own benefit. But, unlike Russia, China has avoided brazenly crossing internationally recognised borders. Yes, it has pushed hard at boundaries in the Himalayas and the South China Sea. But it has reserved its harshest aggression for areas clearly within its territory, such as Hong Kong and the Xinjiang region, and its strongest threats for the one place, Taiwan, where the Cold War left some level of ambiguity.

This is another legacy of the Manchurian Incident. The direct violation of an international land border remains an uncomfortable prospect for the Chinese.

China’s remembrance of the Manchurian Incident raises one more question: how do its current leaders believe the international community should have responded? In general, they take the position that disputes should be settled through dialogue and negotiation, rather than military action. They pour scorn on American interventions, such as in Afghanistan. Given this, it’s harder for China’s leaders to argue that, after the League of Nations’ attempts to dissuade Japan failed, the international community should have taken stronger military action in 1931.

To be sure, America’s interventions in Afghanistan and Iraq had their own dynamics; they were by no means repeats of the Japanese invasion of Manchuria. But it’s striking that, for China, the Manchurian crisis of 1931 remains such an important cause for national remembrance but doesn’t yield easy lessons for reflection, let alone obvious analogies for dealing with today’s geopolitical challenges.