If you have all of these, as I do, then you are ready to attack. You will assault the enemy only if you have the following: sufficient supplies and troops, siege equipment (battering rams, siege towers, etc.), siege weapons (catapults, trebuchets, ballistas, etc.). This choice will send a message to the captain or general of the siege to attack. The third and my favorite choice, is Assault. However, I am a rich and powerful king, and can afford almost anything, from golden thrones to golden cities.
The second option would be the best for one who can’t afford the state of the art technology. Two, you are building siege towers, ladders, or battering rams from the forests surrounding the besieged city. One, because you don’t have the guts to fight the enemy, and just want to starve them out. If you do not understand, I will explain. Maintain the siege, which would be a good option if I was a weakling, and just wanted to wait them out. Lift siege, which I will NEVER do without a good fight. Yet again, I receive a scroll reminding me of the coming battle.