Between the time that RMC Character Law was published and RMC Arms Law was published, it was decided to change the tactical/initiative system.
The original RM2 tactical system may be found here ---> http://www.ironcrown.com/ICEforums/index.php?action=tpmod;dl=item578
As Arioch pointed out, the new/current tactical system can be found in Chapter 3 of the RMC Arms Law.