where traditions were kept in, and passed down through the family. According to Turnbull, the ninja was trained from childhood, as was also common in samurai families. Outside the expected martial art disciplines, a youth studied survival and scouting techniques, as well as information regarding poisons and explosives. Physical training was also important, which involved long-distance runs, climbing, stealth methods of walking and swimming. A certain degree of knowledge regarding common professions was also required if one was expected to take their form in disguise. Some evidence of medical training can be derived from one account, where an Iga ninja provided first-aid to Ii Naomasa, who was injured by gunfire in the Battle of Sekigahara. Here the ninja reportedly gave Naomasa a "black medicine" meant to stop bleeding. With the fall of the Iga and Kōga clans, daimyōs could no longer recruit professional ninja, and were forced to train their own shinobi. The shinobi was considered a real profession, as demonstrated in the 1649 bakufu law on military service, which declared that only daimyōs with an income of over 10,000 koku were allowed to retain shinobi. In the two centuries that followed, a number of ninjutsu manuals were written by descendants of Hattori Hanzō as well as members of the Fujibayashi clan, an offshoot of the Hattori. Major examples include the Ninpiden (1655), the Bansenshūkai (1675), and the Shōninki (1681). Modern schools that claim to train ninjutsu arose from the 1970s, including that of Masaaki Hatsumi (Bujinkan), Stephen K. Hayes (To-Shin Do), and Jinichi Kawakami (Banke Shinobinoden). The lineage and authenticity of these schools are a matter of controversy. Tactics The ninja did not always work alone. Teamwork techniques exist: For example, in order to scale a wall, a group of ninja may carry each other on their backs, or provide a human platform to assist an individual in reaching greater heights. The Mikawa Go Fudoki gives an account where a coordinated team of attackers used passwords to communicate. The account also gives a case of deception, where the attackers dressed in the same clothes as the defenders, causing much confusion. When a retreat was needed during the Siege of Osaka, ninja were commanded to fire upon friendly troops from behind, causing the troops to charge backwards to attack a perceived enemy. This tactic was used again later on as a method of crowd dispersal. Most ninjutsu techniques recorded in