Here's a suggestion, in that regard; Tug of War, as you mentioned earlier.
Defenders start with 75% Defense, attackers with 25% Attack, shown by faction colors on each side, on a single line in the center. As effort is gained, the bar would move slightly to either side, attackers taking down the enemy defenses, defenders pushing back the enemy's attack.
Upon full completion of the territory, it goes on cooldown, OR the faction can sacrifice a region in order to counter-attack said region. This requires a vote from the faction leaders, and could make for a very heated war between factions on one territory.