Was watching a program on TV, and got me wondering, if Britain was deprived of a casus belli in the begining of WWI due to no invasion of Belgium, would they still have joined in the war? Lets assume that there is no Schlieffen Plan as we know it, instead a different plan is devised that respects the Belgian neutrality and invades through Alsace and Lorraine. With handwavium we can also assume that ATL WWI starts in a similar period to ours (1910s) and that the casus belli does not create major changes in the war.
So Germany and Austria (we can either include or ignore Italy, depending on the casus belli) are at war with France and Russia. Does the limit to attacking from German territory hamper the efficiency of the German attack and can they still capture Paris in a relatively short time? Does Britain still enter the war? Could the whole outcome of the Great War be changed?