War caused loss; to shipowners, to seamen, to the nation. Loss of ships; loss of life and limb and of sea chests with their clothing and valuables; loss of trade owing to the slowing of the movement of shipping. By far the most spectacular wartime calamities were the capture of ships and their cargoes by enemy privateers and warships. From the national point of view these losses were usually compensated by captures from the enemy, since destruction for its own sake had not yet been extended to merchant shipping; though this was no comfort to the shipowner whose ship was taken, insurance might spread his losses. It is far from certain, however, that captures, numerous as they were, inflicted as much damage on the shipowning community as other, less dramatic, features of war.

The extent of merchant ship losses in wartime is not easy to ascertain; there was no reason for official recording of it in England, and it was obscured in later wars by the practice of ransom. The Admiralty estimate of losses by the war of 1689-1697, for example, was 4000 ships - a figure almost incredible at first sight. When it is remembered, however, that a great many of these were ransomed - that is, set free at once in return for guarantees of a money payment to the capturer - and that some may have been repeatedly seized, the figure appears a possible one, though not necessarily true. Propagandist exaggeration does appear in some of the figures, but there were a number of attempts to make reliable estimates.

For the war with Spain and France between 1624 and 1629 a vague and incomplete account suggests that losses to the enemy may have exceeded 300 ships, including well over a hundred “large” ships of over one hundred tons apiece. This was a considerable loss for the quite small merchant fleet of the time, and it is unlikely that it was counterbalanced by prizes captured. There were losses, of unknown extent, to French privateers and to Royalists operating from foreign bases, in the late forties.