(a)The Great War, before it was called First World War, because of its extent and impact , generally there would be war between two nations, but in this war Europe was divided into two factions, consisting of 3 countries each initially, and members in Entente increased , this was the period where technology was developing and prior to this tanks were not used much and war was fought on two fronts, western front and eastern front, o western there was Britain ,France fighting Germany and Austria-Hungary and on the Eastern front there was Russia, fighting Germany.
(b)Casualties of World War 1 reached 41 million, including military and civilians, out of which 20 million were dead and 21 million were wounded and in which 9.7 million were military personnel and 10 million were civilians. The Allied Powers have lost about 5.7 million soldiers whereas the Central Powers lost $ million soldier.
(c)Trade restrictions cropped up after the World War came to an end, all the countries implemented protectionist policies, global trading system was ripped apart and later in 1929-30 there was the great depression, where all the countries suffered economically. The War demonstrated how important income tax was to a nation, with so much human loss that the war has brought ,prior to the war top tax was 7% in US and post war it reached 77%. there were many restriction son movement of people, they couldn't have done it so easily, and tourism does account to economic growth and it just dropped to minimum at that point, no tourism no migration. It was in 1993, that trade reached the level of attainment, similar to that of 1913, and international flows of capital in 1996.