I assume that you are asking about the crisis in Manchuria in the early 1930s. I will base my answer on this assumption.
The crisis in Manchuria in the early 1930s happened because Japan wanted to have more of an empire in East Asia. Ever since the Russo-Japanese War of 1904 and 1905, Japan had felt that it deserved to be a major power in that region. Japan was not pleased with the way that its ambitions were being thwarted by European colonial powers and the US.
In the early 1930s, moreover, Japan was in economic crisis. The coming of the Great Depression had harmed Japan’s ability to export. Therefore, the need for an empire to exploit economically was very strong. The Japanese military, in particular, felt the need to expand for economic and nationalistic reasons.
Japan had a strong presence in Manchuria, in what is now the northeastern part of China. Japan essentially controlled that region, but it wanted more formal control of the area and it wanted control over more of China. For this reason, the Japanese military created a crisis in Manchuria. Some Japanese officers planted explosives near a railroad, blew them up, and blamed it on the Chinese. The Japanese then attacked the Chinese in retaliation and the crisis began.