Both the Former and Later Han dynasties had military conscription. All able-bodied men became Regular Conscripts (cheng-tsu) at the age of twenty-three. For one year, they were trained in their home commanderies as Skilled Soldiers (ts'ai-kuan), Cavalrymen (chi-shih), or Sailors in Towered Warships (lou-ch'uan shih), the type of training depending on the localities. Next, they served for one year as Garrison Conscripts (shu-tsu), either as Guards (wei-shih) under the Commandant of the Guards in the imperial capital, or as Guards at the courts of kings, or as troops in the commanderies and at the frontier. When the two years of military service had been completed, the men were discharged and sent home to resume their civilian lives. They henceforth formed a Militia (chia-tsu) which in Former but not Later Han times was called up for further training normally each eighth month (see pp. 94, 96), and which was mobilized during emergencies. From the age of fifty-six, they were excused from further duties. Only certain nobles had statutory exemption from conscription. Those belonging to ranks 4–8 did not have to perform any service in their localities, and those of rank 9 and higher were exempted from all military duties. In addition, each man could free himself from conscription by paying the military tax (keng-fu), or, at times, by presenting to the government grain, horses, or slaves (Han chiu-yi B:6b;Han-kuan yi A:37a).