1. Account for either the defeat of the Central Powers in the First World War or the Axis Powers in the Second World War

2. Central Powers-Germany, Austria Hungary and the Ottoman Empire
Failure of Italy to enter the war on the side of Germany and Austria-Hungary. This was a psychological blow and a bad omen for victory.
Failure of the Schlieffen Plan-Germany was now in a two-front war with all the negative implications that implied.
The war on the western front became a war of attrition that Germany could not win. Trench warfare (defensive) replaced a war of mobility that favored Germany (offensive).
British naval blockade of German ports prevented new supplies of food and fuel to the civilian population.
Germany had to resort to unrestricted sub warfare that brought in the United States on the side of the allies.
Austria-Hungarian Empire had to divert troops to fight Italy and made a poor showing in the war against Russia. Slavic groups in the empire preferred to join the allies.

3. Loss of the Axis Powers in WWII?
Hitler tried to repair mistakes of the Kaiser in WWI. Murder of Austrian Chancellor Dollfuss, Anschluss and the Pact of Steel guaranteed Mussolini would not back out of this alliance. Hungary would join forces with Hitler as Hungary had experienced the reality of a short-lived Communist regime after WWI. Italy would secure the Mediterranean countries and oil assets in the Middle East. Italy did not have the military or the will to accomplish these tasks. Count Ciano, the Italian foreign minister, never bought into this plan.
Germany was defeated in the Battle of Britain (1940). Germany suffered a huge loss of aircraft. (That would negatively affect the Soviet campaign.) Britain could now be used as a staging ground to later invade the continent. The Hess flight to Scotland revealed the psychological defeat of Germany.
Germany was locked into another two front war-the unnerving cooperation of Vichy France on the western front and the unrelenting drive of the Soviet Army on the eastern front.
British and U.S. naval forces harassed German supply lines. The aerial bombardment of German cities demoralized the civilian population and prevented re-supply of food and fuel.
British colonies and commonwealth countries came in on the Allied side to help defeat the Axis Powers
Japanese attack on Pearl Harbor brought the tremendous resources of the U.S. into the war both in Europe and the Pacific.
Japan, Germany and Italy lacked domestic oil supplies. Germany was unable to secure oil supplies in the Soviet Union and the Middle East. Oil was a requirement for mechanized warfare (blitzkrieg).
Strong resistance movements particularly in France and Yugoslavia tied up German troops in the occupied countries. Many of these resistance movements were led by the Communists. (Governments-in-waiting for the defeat of Germany.)
The opening of the North African campaign(1942) further diverted German troops to aid Mussolini.
German leaders were engaged in an intensifying civil war at the same time they were on the offensive in Europe while Soviet leaders had ended their “War against the Peasants.” The Soviet Union was now entirely focused on the defense of the “Fatherland.”