In Europa Universalis II, White flag tourism is a tactic for exploring terra incognita in an enemy country and its surrounding provinces, using normal armies. White flag tourism exploits noncombatant status of land units. As such, it is usually only possible after a war with the enemy. Against pagans, you might initiate the war specifically for this purpose; otherwise it's usually too costly in badboy and/or stability, so you'll only want to do it as a coda to a war declared for other reasons.