What does that mean?
IADs are not to be confused with IEDs (Improvised Explosive Device).
IADs is an Immediate Action Drill. The purpose it to build team 'muscle memory' for what to do in the event of a certain kind of attack. In practice, it means setting up your team in a way that simulates combat, and running through rehearsals of who does what. Depending on your resources, you'd start off doing it with no ammo, then with blanks, then with live rounds. This teaches a number of useful things, such as how not to shoot your buddy or get shot by him. It also makes you take time to realize that changing mags, destroying equipment, and carrying your 'wounded' teammates takes more time than you'd think.
The scenario variations are numerous, and they get really hairy once you start throwing in complications like 'vehicle disabled', 'man down', or 'leaders down' (that's always a fiasco the first couple of iterations).
The upshot of all this is that in the event of contact, you'll know what to do and what your buddies are doing. Once you as a team start getting good you learn how to keep a steady volume of fire without burning all your ammo or slowing your escape.
Well stated.