Three terrorist plotters led a plan to set off eight suicide bombs which could have been bigger than the July 7 London attacks, a court has heard.
Irfan Naseer, 31, Irfan Khalid and Ashik Ali, both 27, are accused of being "central figures" in the extremist plot, jurors at Woolwich Crown Court were told.
Prosecutor Brian Altman QC said: "The police successfully disrupted a plan to commit an act or acts of terrorism on a scale potentially greater than the London bombings in July 2005 had it been allowed to run its course.
"The defendants were proposing to detonate up to eight rucksack bombs in a suicide attack and/or to detonate bombs on timers in crowded areas in order to cause mass deaths and casualties."
All the men are accused of engaging in conduct in preparation of terrorist acts, which they deny.
Naseer is accused of five counts of the offence, Khalid four and Ali three, all between Christmas Day 2010 and September 19 2011.
For Nasser, from Sparkhill, Khalid, from Sparkbrook, and Ali, from Balsall Heath, all in Birmingham, this is alleged to have included planning a bombing campaign, collecting money for terrorism and recruiting others for terrorism.
Nasser and Khalid are also accused of travelling to Pakistan for training in terrorism and it is alleged that Naseer also helped others to travel to the country for the same purpose.