The time had now come for the Germans and Austrians definitely to assume the offensive.  A strategic blow in Galicia imperiled the whole Russian front and compelled a general retreat of the Russian armies in Galicia and Poland.  In June both Przemysl and Lemberg were recaptured by the Central Powers.  By September all of Russian Poland had been conquered.  Russia had lost 65,000 square miles of thickly populated territory.  But the land was so thoroughly plundered by the German conquerors that many of the people died of starvation.

BULGARIA ENTERS THE WAR.—­The sympathies of the Bulgarian government had been with the Central Powers from the beginning of the war.  Bulgaria had not forgiven the neighboring Balkan states for their treatment of her in the second Balkan war (1913).  Against Serbia her feeling was particularly bitter.  The Allied disaster at Gallipoli and the military successes of Germany and Austria in Poland and Galicia in the spring and summer of 1915 led the Bulgarians to believe that now was the time for them to strike.  In October Bulgaria declared war upon Serbia, thus definitely taking her stand as an ally of the Central Powers.

Bulgaria’s entrance into the war was followed by simultaneous invasions of Serbia from Austria and from Bulgaria.  Under these blows the Serbians were crushed.  Together with her neighbor and ally, brave little Montenegro, Serbia was overrun by her enemies.  The cruelties inflicted upon the Serbian population by the invading Bulgars are said to have been fully as horrible as those which had taken place during the conquest of Belgium in 1914 and of Poland in 1915.

There was serious danger that the government of Greece would follow the lead of Bulgaria and also enter the war on the side of the Central Powers.  This was prevented by two things.  In the first place, a majority of the Greek people favored the cause of the Allies and were opposed to Bulgaria.  In the second place, the Allies promptly landed an army at Salonica.  Later on, they removed Constantine, the pro-German king of Greece, and placed his son Alexander upon the throne.

THE EAST AT THE CLOSE OF 1915.—­On the eastern front 1915 had been a year of failure.  The Gallipoli campaign had been a humiliation for the Allies.  The Russians had been driven from Russian Poland and from the Austrian province of Galicia.  Bulgaria had joined the Central Powers, linking Austria-Hungary with Turkey.  Serbia, the country whose quarrel had been the occasion of the whole world struggle, had been conquered by the enemies of the Allies.

ITALY ENTERS THE WAR.—­In May, 1915, Italy declared war upon Austria, and more than a year later upon Germany.  Her reasons for this action were:  (1) her old enmity toward Austria; (2) her desire to annex the neighboring territory inhabited by Italians, but ruled by Austria; and (3) her feeling that Austria was opposed to Italian interests in the Balkans.