RUMANIA has girded herself, like a medieval castle, with a vast moat stretching for 750 miles along its northern and western borders which, at the moment of invasion, can be turned into a river of flaming oil. For more than a year 150,000 Rumanians worked to construct the system of canals, locks to regulate the flow of water at various points, storage tanks for oil, and valves from which the oil can be released on the surface of the water and set ablaze, raising a wall of fire between the defenders and the invaders. There are three main sections of the moat, the longest running about 400 miles from Hotin on the River Dniester to Cetatea Alba on the Black Sea. The canals are fifty feet wide and twelve feet deep, connected with the Dniester and three of its tributaries to use their water and to form a continuous channel to the sea. This section divides the Rumanian province of Bessarabia from Soviet Russia. A second section runs from Hotin to Vijnita, connecting the Dniester and the River Prut, about 100 miles long. This part forms a barrier against what formerly was Polish territory, at a point from which either Germany or Soviet Russia might strike south into Rumania. Western Rumania is guarded naturally by the Carpathian mountains, but south of them the moat resumes in a 250-mile series of canals along the Hungarian frontier from Satu- Mare to Arad, using the waters of the Szamos, Crisul and Maros rivers. In addition to the moat of fire, the outbreak of war would be a signal for closing the steel gates which form tank barriers at the highways from Hungary into Rumania. Back of the canal system are trenches, fortifications and “pill boxes” connected with underground corridors. One section of the canal system was tested not long ago in a realistic rehearsal of a large-scale invasion at the Hungarian frontier. Crude oil was turned into the moat and set ablaze, while the fortifications were pounded heavily with artillery. The defenses fulfilled the expectations of the military experts. One especial advantage of the use of oil is that it freezes at much lower temperature than water and therefore could be used in the moat even during rigorous winters characteristic of southeastern Europe.