What was the Schlieffen plan?

The Schlieffen plan was devised in 1897, years before the outbreak of the First World War in 1914. The plan was based on the assumption that Germany would be at war with France and Russia at the same time and wanted to avoid a war on two fronts. The plan assumed that France would be beaten in a relatively short time and could be beaten whilst Russia mobilised, as they believed it would take a long time for them to do so. Germany believed that they should surprise France by entering through Belgium and then circling back around to fight Russia. However, when Germany entered Belgium, Britain declared war on Germany due to a treaty called the Treaty of London in 1839 that they had with Belgium, where they promised to protect them from any invasions.