i) In January 1917 the Germans proclaimed that they would sink even neutral ships in certain waters.
ii) Lusitania, an American ship was torpedoed by a German submarine.
iii) There was lot of resentment in the USA and President Wilson declared war against Germany.

(a) Battle of Tannenberg
(i) In 1914 Russian forces invaded East Prussia. Germany defeated them decisively. In the battle of Tannenberg Russia suffered heavy losses.
(ii) This caused distraction and helped to relieve the pressure on the western front. The French army made all efforts to drive away the invading Germans.
(b) Battle of Marne
(i) At the Battle of the Marne (early September 1914), the French succeeded in pushing back the Germans.
(ii) Paris was thus saved.
(iii) The battle of Marne is a memorable one for trench warfare.

Russia, France, Britain, Italy, the United States, Belgium, Serbia, Romania and Greece are the nine states that opposed the central powers.

After 1905 Japan took control of Korean domestic and foreign policy. The assassination of a prominent Japanese diplomat provided the excuse in 1910 for Japan's annexation of Korea.

The aim of capitalistic industry was to produce more and more. The surplus wealth thus produced was used to build more factories, railways, steamships or other such undertakings.