 Complete the following phrase:  When World War I began, Germany invaded neutral Belgium and Luxembourg as part of the Schlieffen Plan, trying to take Paris quickly. The threat to France caused Britain to enter the war; it used the 1839 agreement as justification. The Belgian army is remembered for their stubborn resistance during the early days of the war, with the army  around a tenth the size of the Germany Army  holding up the German offensive for nearly a month, giving the French and British forces time to prepare for the 