In 1931, Japan launched September 18 Incident, after which Zhang Xueliang left Shanhaiguan without firing a single shot. So Japanese easily occupied entire Northeast region. On March 1, 1932, with support of Japan, a puppet Manchukuo was created with its capital in Changchun. In September 1932, Japan and puppet Manchuria signed Manchukuo Protocol, and Japan officially recognized puppet Manchukuo. Looking at world of that time, most countries were still suffering from the economic crisis, and they had no time to look around, so they could only indulge in what Japan was doing.
After creation of puppet Manchuria, Nationalist Chinese government strongly opposed it. The reason Japan is setting up a puppet Manchu government is to try to separate Manchuria from China and avoid being obstructed by League of Nations. At same time, this measure of "using China to rule China" will help alleviate rebellious moods of Chinese people and reduce pressure on Japanese. The independence of Manchuria is only Japan's plan, and Japan is also trying to make Mongolia independent as a buffer zone between Japan and Soviet Union.
The so-called "weak countries have no diplomacy", after creation of puppet Manchuria, it was recognized by more than 20 countries of world. In early days of its creation, no one in world wanted to recognize puppet of Manchukuo. In 1936, three fascist countries - Germany, Japan and Italy - formed Axis powers, after which all fascist countries, led by Germany, declared their recognition of puppet Manchukuo. Such countries also include Spain, Romania, Bulgaria, Hungary, Slovakia, Croatia, Dominica, etc. With development of World War II, more puppet regimes were installed and they all recognized each other, such as Vichy France, puppet national government of Van and Provisional Government of Free India. Finland and Thailand, which took position of cooperation with fascist countries, also recognized this.
The Soviet Union, which has always been considered main anti-fascist country, repeatedly pursued policies during World War II that were detrimental to China. In 1934, USSR and Japan signed "Japanese-Soviet Non-Aggression Agreement", simultaneously recognizing Manchukuo as a puppet. In addition, Japan also recognizes so-called "Mongolia". The Soviet Union always wanted to create independence of Mongolia, and Japan always wanted to create independence of Northeast China, so two "fascist" countries converged in confusion. Only with outbreak of World War II, Soviet Union abandoned puppet Manchuria.
In February 1945, three giants - United States, Soviet Union and Great Britain - held Yalta Conference, at which issues of Soviet Union's war against Japan and organization of post-war world were mainly discussed. At this time, Japan is at limit of its capabilities, and large American bombers began to bomb Japan 24 hours a day. However, United States still hoped that Soviet Union would fight against Japan in order to relieve pressure on United States. However, Stalin used "independence of Mongolia" as a condition for sending troops and forced government of the Republic of China to sign it.
The facts have proved that war in Far East does not need participation of Soviet Union at all. As long as two atomic bombs are dropped by United States, Japan's million-strong Kwantung Army in China can only obediently surrender. The United States invited Soviet Union to fight against Japan, expanding Soviet Union's sphere of influence, and it was Americans who picked up stone and shot him in leg. As Soviet Union fought against Japan, Mongolia also broke away from China, China eventually regained Northeast but lost Mongolia.
Although Soviet Union made a great contribution to anti-fascist war, it hurt interests of many countries, such as Finland and Poland. It can be said that before outbreak of World War II, Soviet Union and Germany did not differ much in their essence.