public Iterator<Long> getAllUnits(Long nation) {
Set<Long> retUnits = new HashSet<Long>();
Iterator<Unit> allUnitsIterator = getUnitIterator();
while (allUnitsIterator.hasNext()) {
Unit currUnit = allUnitsIterator.next();
if (nation.equals(currUnit.getOwner().getID())) {
retUnits.add(currUnit.getID());
}
}
return retUnits.iterator();
}