jats:pThis paper explores the multi-faceted nature of the spiritual geopolitics that shaped Cromwellian foreign policy in relation to the Western Design of 1654-5. It stresses the central importance of Protestant religion as a motivating force and argues that the failure of the Design was interpreted in religious terms just as much as its original aims had been. A number of motives combined to drive Cromwell into launching the Western Design. These included: the ‘Elizabethan’ tradition of English anti-Spanish policy; the pursuit of England’s imperial/colonial interests in the Caribbean; an attempt to strengthen England financially by weakening the Spanish economy; the search for security within Europe by allying with France against Spain; and, underpinning all these, the launching of a Protestant crusade against a power that Cromwell regarded as England’s ‘providential enemy’. The failure of the Design in the summer of 1655 was perceived in similarly religious terms. Just as recent scholarship on Britain’s internal conflicts of the 1640s has emphasised the central role of religion and its inseparability from other issues, so the same phenomenon is evident not only in the motives for the Western Design but also in how its defeat was perceived and interpreted.</jats:p>