The Manchurian operation was a strategic offensive operation by the Soviet Army and troops of the Mongolian People's Revolutionary Army during the Soviet-Japanese War...
The invasion of Yugoslavia, also known as the April War, was a military operation of the Axis countries (Germany, Italy, Hungary) against Yugoslavia during...
The Norwegian operation was a military operation of Nazi Germany against the Norwegian Kingdom, beginning on April 9, 1940, and lasting until June 8....
In the Medieval period, every kingdom was at war, everyone was fighting against everyone and it was just a mess.
As technology developed a lot of things changed.