before
The assassination of Franz Ferdinand was like the lighting of the fuse that set off WW1. Many European countries had new military technology and were anxious to test it out. On top of that, Europe during that time was a confusing mix of alliances, so when Ferdinand was assassinated, it provided the opportunity for a war that most European countries thought would only last a number of months.
during
Christmas truce during world war I was the temporary cessation of fighting on Christmas eve and Christmas day. When nations were at war, soldiers were willing to fraternise, meet at no man's land, exchange gifts etc. The celebration was intense in 1914 when there were hectic efforts for an end to the war. Truce was observed on Christmas days in the subsequent years of the war as well, but the celebration was less intense and soldiers were often warned against making close contacts. This highlighted the basic good in man. This showed that there was no enmity between man and man and that the soldiers were only performing their duty while shooting at each other.
after
After the war the United States wanted to forgive Germany and allow it to rebuild economically, however England and France insisted the Germans be punished and forced to pay war reparations. The payments bankrupted Germany and the German people were thrown into poverty and starvation. The desperate conditions brought on by the treaty was what ultimately gave rise to the Nazi party and Hitler as they promised Germany that it would be rebuilt economically and militarily. Hitler also promised that lost territories would be reclaimed.