Between 1995 and 1997, the Bandidos and Hells Angels fought a turf war in Finland in connection with the wider Nordic Biker War. On 27 September 1995, Hirsma was assaulted by members of the Hells Angels and Cannonball MC – a Hells Angels-affiliated club – outside a Helsinki courthouse where he was attending the trial of Kai Tapio Blom and Antti Tauno Tapani, two Bandidos convicted of an anti-tank rocket attack on the Hells Angels' clubhouse two months before. He was sentenced to over a year in prison in June 1996 for firearms offenses and the August 1995 theft of a Hells Angel's colors. Hirsma was sentenced to an additional nine months in prison on 12 July 1996 after being convicted of inciting a Bandidos underling to throw a grenade into the Hells Angels' clubhouse on 18 May 1996. The attack was carried out as retaliation for the murder of Bandidos vice-president Jarkko Kokko, who died on 17 March 1996, sixteen days after being shot by suspected Hells Angels members. In November 1996, Hirsma was attacked and beaten in Sörka Prison amidst a struggle for control of the prison drug trade fought between the Bandidos and a rival group. Hostilities between the Bandidos and Hells Angels came to an end in September 1997 when a truce between both groups was brokered. Since the end of the biker war, the once-rival clubs have operated in parallel rather than competing with each other.