This entrance of Japan into the war introduced a factor fraught with unknown possibilities. Unlike the other enemies of the Teutonic alliance, Japan had nothing to fear for her home territory or her possessions. Secure from attack, she was able to devote all her energies to the task of driving the Germans out of the Far East. By this accomplishment she not only fulfilled the terms of her alliance with Great Britain, but strengthened her own supremacy in that quarter of the globe. Tsing-tau, since its occupation by the Germans, had been like a mailed fist brandished in her face. Since Japan's victory over Russia no other European power had occupied a position on the Asiatic coast that offered a threat comparable to this German stronghold. Also, it was only human that the Japanese remembered how Germany compelled them to abandon many of their fruits of victory in their last war with China. The unknown factor of her participation was just how far Japan would go in aiding her new allies. The military and naval potentialities of the Island Kingdom when the war started were greater than ever before. She was twice as strong as when she went to war with Russia. Her navy was sufficiently formidable to resist, in home waters at least, that of any other power except England. Her army, twice proved during recent years against the soldiers of Russia and China, was steadily increasing its size and equipment. Her predominant position in the Far East was absolutely assured. The Japanese army, based to a certain extent upon the German model, numbered at the outbreak of the war somewhat over 250,000 men of all ranks. This was its peace strength. Military service was obligatory upon all able-bodied males between the ages of seventeen and forty. This law made available each year 550,000 men, but in practice during times of peace the annual conscription amounted to only 120,000 men taken by ballot from among the number eligible. The total effective military strength of the Empire was estimated at a million and a half trained soldiers. The army was divided into nineteen divisions, four independent cavalry brigades, three independent field artillery brigades, six regiments of heavy field artillery and a communication brigade. Each divisional unit consisted of two infantry brigades of six battalions each, a cavalry regiment (three squadrons of 120 men each), a field artillery regiment (six batteries of six guns), and a battalion of army service corps. A battalion of mountain guns was attached to certain divisions. Thus the army on a peace footing consisted of seventy-six infantry regiments (228 battalions), twenty-seven regiments of cavalry. 150 field batteries, nine mountain batteries, nineteen battalions of garrison artillery and nineteen battalions of engineers. When the reserves were summoned to the colors the Japanese system provided for an indefinite increase in the number of battalions for each regiment.