Autonomy is bought, in navies as elsewhere, on an implicit promise about people. A vessel that no longer enters the minefield does not need the crew that used to accept that risk; a vehicle that swims a pre-programmed search does not need the operator who used to steer it foot by foot. The promise is rarely written down in those terms, because it does not have to be. It is carried in the arithmetic of a fleet plan, in the assumption that a smaller ship’s company multiplied by a constant number of hulls yields a smaller bill, and in the political expectation that technology will relieve armed forces of a recruitment problem they cannot otherwise solve. Mine warfare is the European domain in which that promise has moved furthest from prospectus into practice, and it is therefore the domain in which the promise can be tested rather than debated.