Most IBDP students have a clear understanding of Japanese participation in the peace talks after World War I.  Margaret Macmillan’s Paris 1919 very effectively illustrates Japanese goals of racial equality and great power status, and many historians look at World War I as a means of further subjugating the Chinese but little time or effort tends to be given to Japan’s actual military participation in World War I.   Consider the following questions: What interests did Japan have that led to its participation?  How did it justify entering the war?  How important was its participation to the outcome of the war?

Japanese leadership was divided on what to do when war broke out in Europe in August 1914.  The Japanese military had modeled itself after the Prussian army and there was a lot of sympathy among Japanese intellectuals for the Germans.  On the other side were officers in the Japanese navy who wanted to honor the 1902 Alliance with the UK that had been renewed in 1911.  It was these officers who prevailed and on  15 August, the Japanese issued an ultimatum to the Germans: they had to remove all warships from Chinese and Japanese territorial waters and give control of its naval base of Tsingtao to the Japanese by 23 August.

The British had asked for the assistance of their lone official ally: while they did not ask for a declaration of war they did ask the Japanese to find and bring about the surrender of armed German ships in the Pacific.  This allowed the UK to concentrate its navy in the Atlantic, an idea that was considered very important to the conduct of naval warfare at the time.  The Japanese used its alliance with the UK as its pretext to send the ultimatum to the Germans.  Germany did not respond to the ultimatum, so on 23 August the Japanese declared war on Germany and began naval preparations.  It launched an attack on Tsingtao, and the Germans surrendered on 7 November 1914.

The Japanese had already violated Chinese neutrality in this action, and they did not cease there.  After taking Tsingtao, they then proceeded to occupy all of Shantung province (formerly Germany’s sphere of influence), and Japanese troops returned home by the end of 1914. For the Japanese in China, the war did end by Christmas 1914.

In addition to Shantung, the Japanese quickly seized all German colonial possessions in the Pacific: the Caroline, Mariana and Marshall Islands were all taken with relatively little resistance. This gave the British freedom of movement in the Pacific, and it allowed the Russians to concentrate their navy and armies in the west.

Japan never sent its army to Europe, but its navy was dispatched.  In 1917 Japanese ships were used to transport British and French troops through the Mediterranean Sea to the Middle Eastner and African fronts.  Although they did not participate actively in any battles, they freed the British navy to use its forces in similar ways in the Atlantic, where submarine warfare made such escorts increasingly necessary, and they escorted 800 ships that carried 700,000 men to their destinations.

Thus, Japan’s military contributions were small but they were significant in their own ways to the outcome of the war.  Japan allowed its allies to concentrate forces elsewhere as they did not have to worry about jeopardizing their colonial possessions in the Pacific and East Asia.