Civilization V is a video game in which the player controls a civilization through history, trying to win through culture, diplomacy, or sheer military power. I tend to try for the former but often end up with the latter, since a strong military is an easier solution to pretty much all the problems that come up in the course of a game. Are there no iron deposits in your kingdom? You could spend an arm and a leg trading for iron with the computer players, or you could just build some soldiers and conquer the nearest enemy territory with an iron mine. Annoyed with one of the decisions of the United Nations? You could spend hours in careful negotiation to reverse the policy, or you could shake things up and declare war on the civilization hosting UN conferences.
I would imagine these tactics work better in Civ V than in real life. One thing that personally encourages me to warfare in Civ V is the snarky diplomatic dialogue used by all the leaders. For example, in a recent game, the Incas, while maintaining a friendly front, were constantly sending spies to steal my technologies. Whenever an Incan spy was caught, I would have a meeting with Pachacuti, the Incan leader, and he would dramatically stagger off his throne and drop his scepter in dismay before deeply apologizing for the actions of his spy and promising it wouldn't happen again. However, without fail, another Incan spy would be caught just a few turns later. Eventually, one is inclined to conquer the Inca just so you don't have to see Pachacuti again. Another interesting thing about computer player leaders is that they don't get less humble as they get less powerful-- kings with only one city and completely obsolete technologies make demands as if they were superpowers.
In the end, then, war is the most exciting and effective activity available. I suppose that's what happens when only one civilization is allowed to win.