How Prussia constrained France's overseas commitments

Franco-Prussian relations are presented as the main constraint on a larger French deployment to Mexico. Both powers watched for a possible European confrontation. Overseas campaigns usually ranked below European security in their governments' priorities. France's extensive land borders meant that war in Europe would draw resources home and leave overseas forces increasingly dependent on what they already had. In the British comparison, overseas wealth paid for European conflict that kept rivals occupied while Britain expanded elsewhere.