The inquests into the deaths of 21 people who were killed by two IRA bombs began with a minute's silence held in memory of the victims.
A third bomb, jurors were told on Monday, was planted near a bank in the city but failed to detonate.
Peter Thornton, the coroner, told the jurors they would hear evidence of how the two bomb blasts ripped apart two pubs on what was a "perfectly ordinary evening", in November 1974.
The inquest will hear evidence alleging that British security forces may have had prior warning about the attacks, widely thought to have been carried out by the provisional IRA.
Evidence likely to come before jurors includes an "overheard" conversation which took place in a prison two weeks before the bombings, which injured 220 people.
"At 8pm that evening, it was a perfectly ordinary evening in the two pubs, a film was showing at the Odeon cinema but just after 8.15pm, all of that changed," Mr Thornton said.
"Moments later there was an explosion at the Mulberry Bush, and just minutes later a second explosion at the Tavern In The Town.
"They were massive explosions.
"After hearing the evidence you may conclude the bombs were brought and planted in such a way that extensive loss of life, injury and devastation, would have been caused," he said.
"They were planted in enclosed spaces in busy pubs, where there were many people.
"You may be asked to determine whether those who died were unlawfully killed."
Mr Thornton said that throughout 1973 and 1974 there were over 50 incidents involving bombs and incendiaries "in and around Birmingham" but after the pub bombings, "the campaign in the West Midlands stopped".
He told the jury that they would have to consider whether the IRA called off its Midlands campaign because of the "outrage of civilian deaths on this scale" or "some other reason".
The only men to ever stand trial over the bombings, the Birmingham Six, were freed on appeal in 1991.
"Nobody is on trial here, an inquest does not decide matters of criminal or civil liability, and this is not a question of attributing blame to any individuals," Mr Thornton said.
The inquests are being held in Birmingham after years of campaigning by relatives of the dead.
Many hope for a full account into the circumstances of what happened during the bombings.
Hearings will continue on Tuesday and Wednesday, while on Thursday, the jurors will be taken to the former sites of the pubs.
Additional reporting by agencies
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