Athens and Sparta
There were not only two countries.
The roots of the war started between two Grecian cities, Epidamnus and Corinth, in 436 BC.
Germany and England .
The main countries involved in the Cold War were the US and the USSR.
The Peloponesian Wars were a series of three wars between the Delian League led by Athens and the Peloponesian League, led by Sparta. In the end, Sparta triumphed. Although many cities fought in the war, Athens and Sparta led the two sides. Hundreds of the Greek city-states were embroiled, whether they liked it or not, in the 27-year war. The war was between Sparta and its allies and Athens and its empire.
New France and Great Britain are the two countries involved in the French and Indian War. It is also known as the seven year war.
Most Asian countries were involved in World War 2
England and France
The Soviet Union and the United States .
Yugoslavia and Kosovo. This is wrong the two countries involved from WWII to 1991 was the United States and Russia (USSR).
The First two were Germany and Poland
Primary combatants were US & North Vietnam; especially the air war over the North.