I'm not ignoring the Anglo-Japanese Treaty of 1902, and it's worth looking at the course of events. The Japanese, after winning the Sino-Japanese War, forced the Chinese to hand over Taiwan and the Liaodong Peninsula (not Korea as I said first) to them. The peninsula part of this was reversed by an ultimatum from France, Britain, and Russia. The Japanese were so mortified by this reversal that in 1945 the Emperor invoked it as a comparison to the surrender of Japan at the end of WWII.

The lesson they learned (among others) was not to try and take on all the powers directly. Instead, they cooperated during the Boxer Rebellion and then used the good will out of that to sign the treaty with Britain. That fractured the alliance that had forced to hand back the peninsula. France (who was interested mostly in SE Asia and southern China) would not back the Russians without the British. Effectively, the Japanese had isolated the Russians, allowing them to go after those Russians in 1904-05. The victory there gave them Korea and political and military domination in Manchuria and near dominance in the South China Sea.

The British alliance also brought the Japanese into World War I on the Entente side and they took great advantage of it, grabbing the German island colonies and (in China) the German outpost at Qingdao in the Shandong peninsula (all of which they were given as mandates in the Treaty of Versailles). That made the South China Sea a Japanese lake, particularly important with regards to the Chinese because northern China's sea access to the world went through the South China Sea.

At the beginning of all this, the Japanese had had Mahan's book translated into Japanese as they found it compelling. "“In the preface to the Japanese translation of The Influence of Sea Power, Soejima Taneomi, an influential member of the Privy Council, declared, ‘Japan is sea power.’ He argued, ‘Japanese leaders must carefully study Mahan’s doctrines to secure command of the sea; Japan would then be able to control the commerce and navigation in the Pacific and gain sufficient power to defeat any enemy.’” (Sadao Asada, From Mahan to Pearl Harbor: The Imperial Japanese Navy and the United States (Annapolis, MD: Naval Institute Press, 2006), 4.

You may not consider that a quest for domination, but 1) I do, and 2) your original post ridiculing the idea as "so a-historical and flat-out wrong [that] I am speechless" is revealed as the kind of misguided posturing that is all too common on the Internet (you weren't, for example, actually speechless).

Are you ignoring the treaty with the British in 1902? And certainly the Japanese were not the biggest contributor to the Allied offensive on the Eastern Front of the Russian Civil War, but a junior partner that was probably considered useful for the next decade in annoying the Soviets in Outer Manchuria.

The Wikipedia entry is good enough to start on the complicated story of 1st Sino-Japanese War, to which I might add Korea was a mess, poor Korea. China was far from blameless. And after annexation Korea was treated horribly, especially compared to Formosa/Taiwan.

Yes, the Japanese had ambitions in Korea and Manchuria (iron ore, etc), and pretty much the same trade and market ambitions as the other Imperialists in the rest of China, i.e. Shanghai.

But it was 26 years (1931) until, however covertly approved, the Japanese made any moves south of the Manchurian Railway, the Mukden Incident, and it was controversial and considered nearly disastrous at the time inside Japan. The 2nd Sino-Japanese War was then inevitable, and there were plenty of high-ranking Japanese who knew it was unwinnable. After 1937 there was crazy talk about America being East Asia, but Konoe for one knew it was crazy and suicidal.

I will grant you Korea and Manchuria, within the Great Power imperialism and anti-communism of the 1st quarter of the 20th, but you will have to make a much greater effort to prove to me the Japanese had officially or otherwise, territorial or hegemonic ambitions outside of those areas before the 1930s.

Your comment would be more useful if it was framed less offensively. In any case, 1900 was the mid-point in a decade that started with the Sino-Japanese War, a Japanese victory in which they defeated the Chinese and attempted to annex Korea, and ended with the Russo-Japanese War, in which the Japanese eliminated their (then) main rivals in Asia. During this period, the Japanese were making concerted efforts to increase their control in China, most particularly Manchuria, trying to push back the other empires (as they were pushed back by those powers). That they did not achieve their goals has less to do with their aims then with the resistance of both the Chinese and the other imperial powers.

In 1900? I don't think so.

All the Japanese? I don't think so.

To say that the Japanese wanted to "dominate" all of China in 1900, 5 years before the Russo-Japanese war, 30 years before the Mukden incident, is so a-historical and flat-out wrong…I'm speechless.

On whether the Chinese needed to be "more flexible"; those words were your addition and certainly don't reflect my sense of the situation. In fact, the Chinese were enormously flexible and the western imperial powers were never satisfied.