On 3 August the Belgian government refused a German ultimatum and the British government guaranteed military support to Belgium if Germany invaded. Germany declared war on France, the British government ordered general mobilisation and Italy declared neutrality. On 4 August, the British government sent an ultimatum to Germany and declared war on Germany at midnight on 4/5 August, Central European time. Belgium severed diplomatic relations with Germany and Germany declared war on Belgium. German troops crossed the Belgian frontier and attacked Liège. A week after the German invasion, German cavalry had been operating towards Hasselt and Diest, which threatened the left flank of the army on the Gete. Belgian general headquarters chose Halen as a place to delay the advance and make time to complete an orderly retreat to the west. The Belgian Cavalry Division was sent from Sint-Truiden to Budingen and Halen, to extend the Belgian left flank.