(a) The First World War came to an end in 1919 with the signing of Treaty of Versailles, where many clauses were imposed on Germany, firstly, it had to pay a war reparation of $33 billion, to the Allied powers, for the civic damage that was caused, and then there was the War Clause, which states that Germany was responsible for the whole war,and later clauses were laid on Germany's military , their military personnel and navy was reduced to a very low number and Rhine land was demilitarized.
Germany's boundaries have been reduced , Alsace-Lorraine was returned to France, Eupen-Malmedy to Belgium, Memel to Lithuania,Schleswig to Denmark and substantial eastern districts to Poland. Later stripped Germany of all its colonies as well, Togoland, German SouthWest Africa, German East Africa and got distributed among the Allied Nations.
(b) Recruiting and conscription has started and civilians too entered war, not everyone was a soldier and when the men were away, women were doing the work , driving trucks,delivering post and later they were granted the permission to vote as well, post war.More than 1 million British soldiers were dead in the war, X-ray was invented during this time because of war,and many such like two way voice radios, underwater microphones.
The economy of British has steeped down , because during war British invested everything into the war and most of British's economy dependent on exports and by the end of war, British lost its markets which were gained by Japan and USA during war.