Abstract: A procedure and a novel vessel are provided for breaking ice. The procedure comprises the cyclical steps of firstly pretensioning an ice-sheet by plowing under a portion of the ice-sheet with the bow of an icebreaking vessel; secondly superimposing on that pretensioned ice-sheet, a massive momentum force due to the reaction of an impulse force due to accelerating water rapidly downwardly from within a bow chamber; and finally refilling the bow chamber with water. Preferably the impulse force is created by the high pressure exhaust gases from a combustion chamber, e.g. an explosive combustion chamber being applied directly to the water.