Tarik Hassane and Suhaib Majeed, both aged 22, planned to shoot soldiers at an army base in west London or officers at a nearby police station using a pistol fitted with a silencer fired from a moped. Police said civilians could also have been killed.
Majeed was found guilty of conspiring to murder and preparing for acts of terrorism at London's Old Bailey court last month while Hassane admitted the same charges halfway through his trial.
Both men were jailed for life, with Hassane told he will spend 21 years in prison before being considered for release, while Majeed will serve at least 20 years.
Hassane, a medical student nicknamed "The Surgeon", directed the plot from Khartoum, Sudan, where he was studying, contacting his schoolfriend Majeed whom police said had set up a sophisticated system of encrypted communications.
Hassane was so determined to carry out the attack, he carried on with the planning even after Majeed and other suspects had been arrested.
During sentencing, Wilkie revealed that Hassane had admitted travelling to Syria in 2013, spending time there with a friend who became a fighter and was later killed. Data from computers seized by police showed Hassane had pledged allegiance to IS in July 2014.
