Of all types of battle zone movement, the most difficult to detect has been that of submerged craft; it is not surprising that this mode of clandestine activity is centuries old and was first used offensively over 200 years ago. With the Italians, Japanese, British and German navies all active in the use of one- and two-man submarines, it is not surprising to find them employed in a multitude of daring and dramatic sorties against seaborne, harbour and land-based targets. In this thorough study of the topic (the most comprehensive ever attempted in the English language) Paul Kemp provides ample evidence of the diverse tasks undertaken by the underwater warriors. The reader is supplied with sufficient technical data to understand the mechanics of this element of naval warfare, before being taken on the myriad subversive actions performed by these fascinating crafts. For students of naval history and military intelligence work, this substantial account of midget submarines and their crews will prove a major contribution to an intriguing yet under-published topic.