What were the major issues that distinguish World War 1 from World War 2?

Well, WW1 was more of a failure of the alliance systems set up at the time, where countries that did not even want to fight (Germany and Russia) were drawn into the conflict because of pressure from their allied countries. Kaiser Wilhelm of Germany, and Tsar Nicholas of Russia were actually first cousins and good friends, but they did not belong to the same alliance, and therefore had to fight each other during the war. In WW1 there was less of a distinction between "good vs. evil." WW2 was more of a war of necessity. If the Allies had not challenged the Axis, they would have taken over Europe, and potentially the world. WW2 had a more desperate feel than WW1, and the lines changed more dramatically. During WW1 the war in Europe was based through Eastern France, and Belgium. Though the fighting was very intense, very little ground was actually won or lost. WW2 however, was quite different. The Nazi's used a technique called "Blitzkrieg" to rapidly advance through hostile territory, and with this, quickly and successfully occupied France and many other countries. After France fell, Great Britain, aided by Canada, was left by itself and very near to a German invasion. Luckily, the United States, who were fairly un-affected by the war at that time, joined in on the side of the Allies and helped liberate France, Belgium and other European countries from the Nazi rule. While these countries were being liberated, soldiers began discovering the horrors of the concentration camps scattered throughout Europe, and exposed this to the world.