Changes

The spark was the assassination in Bosnia of Archduke Ferdinand in June 1914, and war between the two alliances soon began.  The secret promises among many countries to defend each other caused them to be pulled into the war, making this the first genuine world war in history.

The spark was the assassination in Bosnia of Archduke Ferdinand in June 1914, and war between the two alliances soon began.  The secret promises among many countries to defend each other caused them to be pulled into the war, making this the first genuine world war in history.

The United States was not involved until 1915, when a German submarine sunk the Lusitania.  That was a British passenger ship carrying many Americans, 128 of whom died.  The American public was outraged.

In 1915, a German submarine sunk the ''Lusitania'', which was a British passenger ship carrying many Americans, 128 of whom died.  The American public was outraged, but still did not support declaring war against Germany.

Congress began to prepare for war.  In 1916, it passed the National Defense Act, which was a military preparedness program that expanded the army, increased the size of the National Guard fourfold, and set up "ROTC" programs for college students to earn tuition in return for military service.  It gave the president the power to mobilize the National Guard in the event of a national emergency such as war.

Congress began to prepare for war.  In 1916, it passed the National Defense Act, which was a military preparedness program that expanded the army, increased the size of the National Guard fourfold, and set up "ROTC" programs for college students to earn tuition in return for military service.  It gave the president the power to mobilize the National Guard in the event of a national emergency such as war.