Intelligence and the Ardennes

Before the offensive, Allied intelligence tried to penetrate German intentions. Several indications, and even warnings (transmitted notably via sources in Berlin), suggested that the main effort might come through the Ardennes — and not across the plain of Belgium, as the Dyle plan assumed. But this hypothesis collided with a deeply entrenched certainty: the Ardennes, a wooded and broken massif, were reputed impassable for a mass of armour.

The Deuxième Bureau and the command had to assess these signals. To take the Ardennes threat seriously and reinforce that sector (held by second-rate units). To stick to the established plan, judging the Ardennes impassable and the main effort to be expected in Belgium. Or to seek further confirmation before overturning the dispositions.

The weight of doctrinal certainties, the difficulty of interpreting contradictory intelligence and the fear of deception complicated the analysis. Yet to be wrong about the axis of the main effort was to place one's best forces in the wrong place — exactly what the Manstein plan sought.