According to the Fortress Ameritrash website, Jim Wallman lives in South London and is known for his sense of humour and knowledge of military technology and history. He started playing games in the 1970s with miniature wargaming icons Paddy Griffith and Donald Featherstone. In the early 1980s, he became involved in Wargame Developments, a English game design group. He is one of the founding members of Chestnut Lodge Wargames Group which is dedicated to the design of new games. He placed many of his game designs online for the general public. In 2005, he organized his one-hundredth megagame with about 150 players and umpires fighting World War II from January 1942 until the end.