 The ships were incorporated into the 1939 Plan Z for the re-equipment and expansion of the Kriegsmarine; while an aircraft carrier, H-class battleships and smaller ships engaged convoy escorts, one or more O-class ships would attack the merchant ships.The O class' design reflected their intended role; a heavy main armament (six 380 mm guns in three dual turrets) for possible encounters with escorting -armed heavy cruisers, enough armor to defend against the same and nothing more, and a high top speed so that they could get away from slower but much better armored capital ships.Although planned and ordered, construction did not progress due to lack of materials and higher priorities for ship construction.