At the present time, when the thoughts and sympathy of many are with our Norwegian friends and allies, it may be of interest to recall certain other occasions on which they have had to face invasion from the sea. Moreover, the fortifications erected in Norway during the sixteenth and seventeenth centuries are of particular interest for comparison with those of this country during the same period, since, doubtless owing to their geographical position, both countries seem to have been influenced only gradually and spasmodically by the developing military science of the middle European peoples, the Germans and Italians.

Most of the artillery fortifications existing in Norway, as described in Festninger og andre militœrbygninger, date from the late seventeenth century or later, but even very brief research at the time of the International Congress of Prehistoric and Protohistoric Sciences at Oslo in 1936 showed that some portions of earlier work still exist at various places, largely incorporated in later defences. No extensive survey of these remains can be attempted here, since the material is not readily available, but the two illustrations of Oslo (Christiania) here reproduced form an excellent introduction to the study of such defences.