AJAX progress indicator - HELP

Dear Digital Point Forum,
I am trying to create a strategy online mmo game based in php mysql and ajax. The problem is that I dont really know ajax and im trying to learn while making the game. So I have the following problem:

Lets say that a user wants to attack with his army consisting of units a, b, c to another user.
The second user will have units e, f, g.
So the first user imports in 3 fields the desirable amounts of this units and hits attack button.
When this button is hit I want to be able to start an ajax operation that will call a php script where the attack algorithm is inserted and appear to the client the outcome.
It will work like this:
=> unit a attacks units e, f, g the outcome appears on the client
=> unit b attacks units e, f, g the outcome appears on the client
=> unit c attacks units e, f, g the outcome appears on the client
=> the total outcome is imported in mysql database

Maybe im asking for much but please giveme some hints on this cause i dont even know how to start, thanks in advance!