Jesus' Donkey: symbol of what, exactly?

Typical Palm Sunday interpretation: Jesus rode a peaceful donkey instead of a war horse to indicate his non-violent intention. However, I've also heard it suggested that donkeys were better animals for waging war on rocky hillsides where horse-drawn chariots were useless--so, donkeys were still a symbol of war, but they represented the indigenous underdog using guerrilla tactics, as contrasted with the big and powerful armies of a foreign invading empire. Perhaps there's room for both meanings--we could imagine the crowds taking the second interpretation (hoping for a violent revolution) whereas Jesus intended the first (as was demonstrated soon after). Or we could take Jesus' act as transforming a symbol of the people's resistance into something even more powerful.