Britain and the war

Explain why Britain was drawn into the war in 1914? 

Why not earlier:

• 1904- Entente Cordialw- agreement between Britain and France- meant they were also on friendly terms with Russia. Broken.
• Later in 1914 when Germany wanted to defeat France then Russia. They attacked France through Belgium which was protected by Britain in the Treaty of London in 1839- broke the Schleiffen plan. 
• Some Historians argue that Britain weren't obliged to join the war and that the Treaty was merely 'scraps of paper'. 
• Russia and France signed the Dual Alliance in 18780 endangered Britin- why they signed the Cordiale otherwise Russia or France could attack.
• Hay-Penceforte Treaty in 1901- America could make a fortified canal in Panamare- America would built it and control it but Britain would supply weapons and troops. 
• Way of building relations with America- they had a much larger Navy. 
• Arbitration with USA- avoided war-…