What conflict triggered between russia and japan?

The conflict that officially triggered the war between the Russian Empire and the Empire of Japan was the Japanese attack on the Russian fleet at Port Arthur, China.

The tensions between Russia and Japan were building on for some time. The reason for that was that both of the countries had expansionist policies and it was for the same territories, Manchuria and the Korean Peninsula. Japan saw Russia as a big threat, especially because it was an ever growing power and it gradually had been expanding its territory towards the east. The negotiations with which Japan wanted to avoid conflict and divide the territories of interest, Korea to Japan and Manchuria to Russia, was not acceptable for Russia. That led the Japanese to make a surprise attack on the Russian fleet at Port Arthur, China, one of the most important places that the Russians wanted to gain. This attack prompted the war between the two empires, taking place Liaodong Peninsula, Mukden in Manchuria, the seas around Japan and Korea, and the Yellow Sea.