The life cycle of stars may be boiled down into a tug of war, lasting billions of years, between two basic forces. In your own words, describe these forces, and identify which of the two eventually "wins" the battle.

Stars are very massive stellar objects, which means that they have a very intense force of gravity. This is the first of the forces entering this "war".

In addition to that, due to the force of gravity that drives the star to contract, the process known as fusion occurs (the union of atoms of one element that results in another element, hydrogen fuses in stars to produce helium). The fusion created in the high temperatures of the center of the star generates an enormous amount of energy (which causes the stars to shine) and a force going outward of the star counteracting gravity, this is the second force in the "war".

In a stable star these two forces (gravity going inward and the pressure created by the fusion going outward) are in balance, preventing the star from exploding or collapsing. But eventually the star exhausts its "fuel" (hydrogen atoms) to produce fusion within it (although stars also fuse helium and other heavier elements, but once the hydrogen is finished the star is near its end), which decreases the force outward from the star, making the force that wins this battle to be the force of gravity.

When the force of gravity wins, the star collapses on itself and from here, depending on the star's mass, several things can happen, such as the star becoming a white dwarf, a supernova, even a black hole.