Traditionally it is very important to be able to delete or disband units in a "Civilization" game. This can be a micromanagement headache or an essential strategic aspect to any particular match, but you generally can't afford to just let huge, obsolete armies stick around. "Civilization Revolution" for iPad is different in this respect. Because there is no ongoing cost for units in the field, the strategy is all in deciding how to handle your old troops. You can ignore them or creatively exploit them to conquer cities, but there is no way to outright destroy your units.
Exploration and Early Warning
Move your excess troops to the outskirts of your territory. If possible, space them evenly in a roughly circular pattern or along the boundaries of your known world's land masses.
Push your troops outward to uncover more territory. If the option is available given the restrictions presented by other civilizations' territories and the map's configuration, spiral your troops outward to evenly reveal the world. The more land they uncover, the more likely they are to run into hostile units and be destroyed.
Position any remaining troops at choke points in the area surrounding your territory once the map is uncovered. They are expendable and will provide your first warnings of invasions from barbarians or competing civilizations.
Hold onto older troops until you have a navy capable of bombardment.
Move obsolete units along the shore with a naval escort that can defend them from modern enemies. Until you reach an enemy settlement, all these units need to do is stay alive.
Soften up any enemy settlement with your powerful naval units and send in obsolete units only when there will be little opposition. In this way it is possible to take over territory using even the weakest of warriors. If it doesn't work, all you have lost is an otherwise useless army.
Tips & Warnings
- If you have no interest in making use of your old units, find an uninhabited island to drop them off. You can put them to sleep and never be prompted to move them again. Unless somebody randomly decides to be aggressive toward them, it amounts to the same thing as disbanding.