The reoccupation of the Rhineland, on 7 March 1936, conventionally referred to as its remilitarization, was one of the few real turning points in modern history. It marked the end of the last vestiges of the ‘Versailles System’ and it has been considered a missed opportunity for calling a halt to Hitler's aggressive designs. It was also a problem which affected the very foundations of the Franco-Polish alliance, a relationship which had a chequered history in the interwar period. For France and Poland, Germany's neighbours, most of all, the reoccupation of the Rhineland would on the surface appear to have been the last occasion on which they might have collaborated to contain Hitler's Germany. This article will attempt to show how much more complex the question was in reality. It examines the degree of mutual consultation and encouragement between France and Poland prior to the reoccupation, and their reactions to it. This episode provides an excellent case-study of how the alliance worked in practice and also throws some interesting sidelights on the European diplomatic scene in this period.