DARKNESS covers the muddy field after a late-afternoon shower. Bare feet splatter in the mud. A martial arts school instructor and his 60 students are panting for breath. They have just warmed up by running three laps around a football-field-sized spot of land in Cemani, Sukoharjo, Central Java.

Joko Sutrisno, 53, the instructor of the school, stands in front of the students. Last Tuesday, he gave an unusual lesson. Not limiting himself to imparti