So what historians have come to call the Phase of the Emergency Committees sprang from the opening phase and from the phase of social collapse. Then followed a period of vehement and passionate conflict against disintegration; everywhere the struggle to keep order and to keep fighting went on. And at the same time the character of the war altered through the replacement of the huge gas-filled airships by flying-machines as the instruments of war. So soon as the big fleet engagements were over, the Asiatics endeavoured to establish in close proximity to the more vulnerable points of the countries against which they were acting, fortified centres from which flying-machine raids could be made. For a time they had everything their own way in this, and then, as this story has told, the lost secret of the Butteridge machine came to light, and the conflict became equalized and less conclusive than ever. For these small flying-machines, ineffectual for any large expedition or conclusive attack, were horribly convenient for guerilla warfare, rapidly and cheaply made, easily used, easily hidden. The design of them was hastily copied and printed in Pinkerville and scattered broadcast over the United States and copies were sent to Europe, and there reproduced. Every man, every town, every parish that could, was exhorted to make and use them. In a little while they were being constructed not only by governments and local authorities, but by robber bands, by insurgent committees, by every type of private person. The peculiar social destructiveness of the Butteridge machine lay in its complete simplicity. It was nearly as simple as a motor-bicycle. The broad outlines of the earlier stages of the war disappeared under its influence, the spacious antagonism of nations and empires and races vanished in a seething mass of detailed conflict. The world passed at a stride from a unity and simplicity broader than that of the Roman Empire at its best, to as social fragmentation as complete as the robber-baron period of the Middle Ages. But this time, for a long descent down gradual slopes of disintegration, comes a fall like a fall over a cliff. Everywhere were men and women perceiving this and struggling desperately to keep as it were a hold upon the edge of the cliff. A fourth phase follows. Through the struggle against Chaos, in the wake of the Famine, came now another old enemy of humanity--the Pestilence, the Purple Death. But the war does not pause. The flags still fly. Fresh air-fleets rise, new forms of airship, and beneath their swooping struggles the world darkens--scarcely heeded by history.