1:35 | John Gannon, a naval gun captain, illustrates the procedure for firing some of the larger ship-mounted turrets.
John Gannon describes a strategy that German U-boats would use to open up Allied convoy defenses in the Atlantic.
John Gannon, a naval gun captain, illustrates the procedure for firing some of the larger ship-mounted turrets.
John Gannon talks about the dangers that would arise from carelessness aboard naval vessels.