A Veteran is an upgrade to units in Civilization II that confers a 50% bonus to Attack and Defense strength (rounded down). Any unit which wins in Combat has a chance to be upgraded to Veteran status.
During the American Civil War, soldiers who had never been in battle were said to have "seen the elephant" after being under fire for the first time. Afterward, they were considered veterans. History shows that well-trained, veteran soldiers are much more likely to survive a battle than inexperienced troops.
Units have a 50 percent chance of becoming Veterans each time they survive a combat encounter. Cities with a Barracks Improvement automatically produce Veteran units, as do all cities under the influence of the Sun Tzu's War Academy Wonder. The attack and defense factors of Veteran units is increased by 50 percent.