He found that the defence problem was in some ways a complex one, whilst in other directions it was simplified considerably by the unique conditions of the new warfare. Owing to the enormous perimeter which had to be defended, the garrison was almost wholly used up in forming a very thin firing-line which was liable to be rushed at any point by strong bodies of the attacking force, as, indeed, he had already seen himself. Given sufficient spontaneous co-operation for a raid, the trenches could be entered without any real difficulty by the survivors of a charge. But once within the defended lines, the attackers were accepted as part of the defence force, provided that their numbers were not in excess of the casualties produced by their onset. Thus the _personnel_ of the trench-lines changed from day to day, dead defenders being replaced by successful raiders whose main interest had changed sides. Under such conditions, the maintenance of discipline was a matter which required the sternest measures. The garrison was always up to full strength; but its members were not a military body in the usual sense, since they changed from time to time as new recruits took the places of the killed. Of _esprit de corps_ in the usual meaning of the words there was not a trace; but its place was taken by the instinct of self-preservation, which seems to have made not a bad substitute. As to the question of ammunition-supply, which had puzzled Hinkinson so much during his experiences in the outer zones, it became simple when once he was inside the trench-lines. There appears to have been a regular traffic by aeroplane between the food-area and the outer world, munitions being imported by air in exchange for food which the air-craft took back on their return trips. * * * * * Readers can now picture for themselves the state of the world after the Famine had done its worst. The great cities which marked the culmination of civilisation had all shared the fate of London; and most of the towns had gone the same road. All the vast and complex machinery which mankind had so laboriously gathered together in these teeming areas had been destroyed by fire. Here and there--in Scotland, in Japan, and in a couple of American centres--Nitrogen Areas were in full activity; and the traditions of pre-Famine times were being kept alive, though with profound modifications; but outside the boundaries of these regions the only human beings left in the world were a mere handful, scattered up and down the globe and existing hazardously upon chance discoveries of food-stuffs here and there. The Esquimaux had a better prospect of survival than most of these relics of civilisation.