The allies disagreed over the treatment of Germany in 1919 because they all had different experiences of war.
France is geographically situated right next to Germany, and had the most casualties and damage, as the battles had largely taken place on French soil . They were old enemies, having been humiliated in the Hall of Mirrors at Versailles with the establishment of the Second German Empire in 1870-1871. The Prime Minister, Clemenceau was the Mayor of Paris during the siege of 1870-1871, where the inhabitants were forced to hunt the local rat population for food. France was also humiliated at the annexation of Alsace-Lorraine. France therefore wanted the harshest penalties on the Germans, and wanted money to help to rebuild the cities, and coal to compensate for the coal and iron ore extracted from Northern France by the Germans, and to prevent a recurrence of World War One. The French were not a big exporter of goods to Germany, so they did not see the economic implications to the German's.
They would be afraid of a Russian Communist revolution in Germany as the revolution could easily spread from Germany to the country next to it.
The United Kingdom was suspicious of Germany's decision to build a large navy, as they feared that they could be under attack. After the end of World War One, the British were keen to remove this threat. Britain's public were fed propaganda about German atrocities, and were keen to enact revenge. However, the British Prime Minister, David Lloyd George, realised that this may not be in Britain's best interests, as France was Britain's traditional enemy, not Germany, and if the French were not under attack, they could come and attack the United Kingdom. Britain was also concerned about the Russians. If there German army was...