European land and airborne systems are absorbing processing, sensing, communications and power-conversion capability into enclosures whose internal volume, electrical supply and external heat-rejection area do not expand at the same rate. The constraint that follows is routinely described as a cooling problem, but that formulation is too coarse to support a procurement decision or an industrial assessment. What matters is narrower and harder: whether a thermal technology allows an electronic load to remain at its required power for the required duration while component temperatures and the platform’s environmental margins hold, or whether it merely carries the same heat to another interface at which an air exchanger, radiator, cold wall, liquid circuit or powered auxiliary remains the binding element. A compact processor, sensor or power module has no operational value at its nominal electrical rating if that rating cannot be sustained once the thermal transient has expired. The question this distinction poses is therefore not whether European suppliers can move heat, which is settled, but under what documented conditions moving it differently converts into sustained electronic power on a defence platform — and what the public record, read to the cut-off, actually establishes about the two European specialists most often named in this field, Calyos of Belgium and APR Technologies of Sweden.