There is no such thing as an object with two sides.
trapezoid
A PLANE has two sides
a trapezoid
Two sides of a quadrilateral can be parallel.
Picture a box with four sides. Fighting on 1 side is one front. Fighting on two sides of the box is fighting on two fronts. Three sides of the box is 3 fronts, four sides of the box (surrounded) is fighting on four fronts. Two or more fronts is a multi front war.
The Federalists and the Anti Federalists
Greeks versus Persians .
Oil
Cease fire is the asking of to stop fighting between two sides which are fighting
The United States was fighting on two sides. On one side they were fighting Germany, and on the other side they were fighting Japan. It technically was the same war but they call it two seperate ones because they happened on opposite sides of the United States.
Gadaffi's supporters (the government) and the rebels.
The term might refer to mediation used between two sides of different cultures, or two sides fighting over some aspect of culture.
the union wanted to stop slavery and the confederates ddidn't
The struggle for independence, the Patriots wanting independence and the Loyalist did not (following England).
The communists.
Union fought to free slaves, Confederate fought to stay slave states.