The first four months of 1915 witnessed a titanic struggle on the Eastern Front, in East Prussia, the Carpathians, Bukovina, and at Przemysl. Both sides suffered staggering casualties that surpass those of the Somme or Verdun the following year. Ironically, the Austro-Hungarians lost far more men trying to save Przemysl than there were in the fortress.
By the late 19th century the US stretched from the Atlantic to the Pacific to the Arctic. From the 1890s though, a new wave of American expansion began that resulted in a vast overseas empire including the Philippines, Cuba, Haiti, Panama, Nicaragua, and more.
By the spring of 1915, the Western Front had bogged down into trench warfare. Allied offensives tried to break the deadlock in spring and fall 1915. The fall offensives were among the bloodiest of the war. After unprecedented bloodletting and use of munitions, the Western Front was still locked in a stalemate at the end of 1915.
On March 3, 1918 the Central Powers (Germany, Austria-Hungary, Bulgaria, and the Ottoman Empire) and Bolshevik Russia signed the Treaty of Brest-Litovsk, ending the First World War on the Eastern Front. The terms were harsher than those the Germans offered in December, and much harsher than the later Treaty of Versailles. The Treaty of Brest-Litovsk was only in force until November 1918, when the Central Powers’ defeat nullified it. But it had a major impact inside and outside Russia.
On April 25, 1915 Australian, British, New Zealand and French forces landed at the mouth of the Dardanelles to capture the Gallipoli peninsular and march on Constantinople. But the Ottoman defenders, including legendary officer Mustafa Kemal, held firm and the Battle of Gallipoli would last for 7 bloody months.
Following the Bolshevik takeover, the communist government under Vladimir Lenin wanted to end Russia's participation in the First World War, transform the country and carry the revolution abroad. But Anti-Bolshevik resistance took hold all over the country and across the political spectrum. Many former parts of the Russian Empire also declared independence and received support from the major powers. There would be no peace and the Russian Civil War had begun.