who was the prime minister during this time?
H. H. Asquith.
History of the United Kingdom during the First World War
On 4 August, King George V declared war on the advice of his prime minister, H. H. Asquith, leader of the Liberal Party. Britain's basic reasons for declaring war focused on a deep commitment to France and avoidance of splitting the Liberal Party. Top Liberals threatened to resign if 
which factor most directly resulted in great britain entering world war i Belgium had won the war for its independence and at the Treaty of London in 1839 Britain with other major powers guaranteed the independence of this nation. On the 4th of August 1914, Germany invaded Belgium and thus Britain stepped in to honor its promise from 1839. when did this war begin? 1914.
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History of the United Kingdom during the First World War [SEP] Asquith as prime minister
On 4 August, King George V declared war on the advice of his prime minister, H. H. Asquith, leader of the Liberal Party. Britain's basic reasons for declaring war focused on a deep commitment to France and avoidance of splitting the Liberal Party. Top Liberals threatened to resign if the cabinet refused to support France—which would mean loss of control of the government to a coalition or to the Unionist (i.e. Conservative) opposition. However, the large antiwar element among Liberals would support the war to honour the 1839 treaty regarding guarantees of Belgian neutrality, so that rather than France was the public reason given.