Although tensions between the Austrians/Germans and the Serbians were running very high prior to any real military engagement, the assassination of Archduke Ferdinand and his wife Sophie in Sarajevo was the one event that gave the Austrians the justification to invade Serbia they were looking for. The Archduke was killed by a member of a secret Serbian military society known as the Black hand.
The actual assassination attempt failed, but as the Archduke and his wife were trying to escape by car, their chauffeur made a wrong turn into a dead end ally, where an unwary member of the Black Hand was given this golden opportunity for stardom.
When Germany invaded Poland.
The breakup of the Soviet Unionvand the destruction of the Berlin wall in 1989
While tensions had been brewing for many months in Europe, one event served as a signal to start World War I. A disaffected Serbo-Croatian separatist assassinated Archduke Ferdinand of Austria in June of 1914.
some say the Truman Doctrine of 1947 was the beginning. Still others say the 1948 Berlin blockaed and airlift signaled the start. 1947-1948
The event that triggered first world war was the assassination of Archduke Franz Fredinand of Austria by a Yugoslavian nationalist Gavrilo Princip. This started a diplomatic crisis which eventually started the conflict.
The battle of Midway
When Germany invaded Poland.
no
Armistice Day signaled the end of World War I.
The coming down of the Berlin Wall signaled the beginning of the end of the Cold War in 1989
Armistice Day signaled the end of World War I.
Invasion of Poland
The assassination of Archduke Ferdinand.
Abraham licon wanting to stop slavery
The dropping of the Atomic Bombs was considered the beginning of the end of World War 2. It did motivate Emperor Hirohito to surrender.
France
Pearl Harbor bombing