His strategy emphasised the importance of striking the first blow, but with an awareness that sunk ships could not easily be replaced, and would replace any officer who could not keep up with the standards he demanded. He gave lectures on naval strategy to which all officers were invited and once again encouraged his officers to bring ideas to him. He offered prizes for essays on tactics and maintained a large tabletop map room with models of all ships in the fleet, where all officers could come to develop tactics. A particular concern was the threat of torpedoes, which Germany had boasted would dispose of the British fleet, and the numerous French torpedo boats. Fisher's innovations were not universally approved, with some senior officers resenting the attention he paid to their juniors, or the pressure he placed on all to improve efficiency.