From S&T #163

ROMAN CIVIL WAR (S&T #157)

When playing Trajan (S&T 145), use all Roman Civil War rules EXCEPT Res
Publica (36); the Late Republic was a very different political animal
fromTrajan's Empire! Be sure to combine specific information from Trajan
regarding Parthians, Armenian, Arabs, and Alani with the general RCW
rules on Off-Map Regions (14), Recruitment (13 & 29), and Clients (15 &
31). The following Trajan rules sections contain the needed information-

(11.10) Off-Map Forces Box ("Roman Empire Off Map Forces Box")

( 17.2) #2 - Roman Off-Map Forces recruitment

(17.3) Parthian Forces recruitment

( 18) & (22) Client Forces

26.6 Disrupted units do NOT count toward the Heavy lnfantry total which
can negate strength loss results. Only good order Heavy Infantry may
serve this purpose.