Hiroshi Isoyama-sensei was born in Iwama and trained a number of years with O-Sensei. He became an officer in the Nihon Koku-Jieitai (Japan Air Self-Defense Force), and prior to his retirement became the chief martial arts instructor for the Japanese armed forces.
His primary students were a group from the Iruma Air Self-Defense Force base. A number of them had trained with O-sensei. They came to Iwama for gasshiku at least once a year, and Isoyama-sensei taught the classes.
These guys were absolutely great! We would normally get up at 5 AM and run up Atago-san (the mountain behind the Iwama town), train hard all day and party hard until the wee hours of the morning. I especially remember a colorful character named Sgt. Asai who had huge biceps that he loved to show off.
Isoyama-sensei had a number of unique warm-up exercises that could get excruciating really fast. Those gasshiku were really challenging.
It was the custom in Japan at parties for people to pour drinks for each other, and not let each other's glasses get empty. The Iruma guys elevated this to a whole new level. Even if someone's glass was completely full (and even had a positive meniscus), someone would offer to pour more, and it was impolite to refuse. Of course we had to drink some to make room in the glass for more.
We would often party until about 2 in the morning, and then get up at 5 and do it all over again. In retrospect, I think the hardest part of it all was getting up in the morning.