‘Magnum est stare in Danubii ripa’, wrote Pliny in his panegyric to Trajan. The significance of his words can only be appreciated by the sight of the Danube's gorges: Struden, Wachau, Devin, Esztergom, Iron Gate, either fairytale-like in their beauty or gloomy and menacing, through which the movements of European prehistory forced their way. The prestige of the great river can be felt in Augustus's proud words protulique fines Illyrici ad r[ip]am fluminis Dan [u]i.Trajan spent the winter of 98 and the whole of 99 with the Moesian armies. He paid special attention to military discipline; together with the army leaders he worked out careful plans for a preventive attack on the Dacians. Some of the measures he undertook, then and later, are in process of being recovered. Relevant items are: 1: The construction of the famous fortified bridge at the old fording-point at Kostol. 2: the mobilization on a war-footing of the military river flotilla. 3: the reorganization of military bases on the northern bank of the Danube. 4: the creation of an intelligence-espionage service. 5: co-ordination and organization of the troops to be used in the assault. 6: a large-scale building programme to provide accommodation for the invasion force and to increase the capacity of ports in the winter months. 7: the modernization and reconstruction of the towing-path along the river, especially the rock-cut sections in defiles. 8: the engineering of navigable canals beside sections of the river with rapids.