For a week the line had been staggering back, fighting savagely to hold their ground, being driven in, time and again, by the sheer weight of fresh German divisions brought up and hurled without a pause against them, giving way and retiring sullenly and stubbornly to fresh positions, having to endure renewed ferocious onslaughts there, and give to them again. Fighting, marching, digging in; fighting again and repeating the performance over and over for days and nights, our men were worn down dangerously near to the point of exhaustion and collapse, the point over which the Germans strove to thrust them, the point where human endurance could no longer stand the strain, and the breaking, crumbling line would give the opening for which the Germans fought so hard, the opening through which they would pour their masses and cut the Allied armies in two.

Now at the end of a week it looked as if their aim was dangerously near attainment. On one portion of the line especially the strain had been tremendous, and the men, hard driven and harassed for two days and nights almost without a break, were staggering on their feet, stupid with fatigue, dazed for want of sleep. Of all their privations this want of sleep was the hardest and cruellest. The men longed for nothing more than a chance to throw themselves on the ground, to fling down on the roadside, in the ditches, anywhere, anyhow, and close their aching eyes and sink in deep, deep sleep. But there was no faintest hope of sleep for them. They had been warned that all the signs were of a fresh great attack being launched on them about dusk, by more of those apparently inexhaustible fresh enemy divisions. The divisions they had fought all day were being held stubbornly by rear-guard actions until the new positions were established; and plain word had been brought in by reconnoitring air men of the new masses pressing up by road and rail to converge with all their weight on the weakened line and the worn-out men who made ready to hold it. Everyone knew what was coming. Company and battalion officers scanned the ground and picked positions for trenches and machine-guns to sweep the attack; Generals Commanding pored over maps and contours and sought points where concentrated shell-fire might best check the masses. And all who knew anything knew that it was no more than a forlorn hope that if once those fresh divisions came to close quarters they could be beaten back. Our men would be outnumbered, would be unrested and worn with fighting and digging and marching continuously,—that was the rub; if our men could have a rest, a few hours' sleep, a chance to recuperate, they could make some sort of a show, put up a decent fight again, hold on long enough to give the promised reinforcements time to come up, the guns to take up new positions. But "a renewed attack in force must be expected by dusk" said the word that came to them, and every precious minute until then must be filled with moving the tired men into position, doing their utmost to dig in and make some kind of defensive line. It looked bad.

But there were other plans in the making, plans figured out on wider reaching lines, offering the one chance of success in attacking the fresh enemy masses at their most vulnerable points, fifteen, twenty miles away from our weary line. The plans were completed and worked out in detail and passed down the chain to the air Squadrons; and Flight by Flight the pilots and observers loaded up to the full capacity of their machines with bombs and machine-gun ammunition and went droning out over the heads of the working troops digging the fresh line, over the scattered outpost and rear-guard lines where the Germans pressed tentatively and waited for the new reinforcements that were to recommence the fierce "hammer-blow" attacks, on over the dribbling streams of transport and men moving by many paths into the battle line, on to where the main streams ran full flood on road and rail—and where the streams could best be dammed and diverted.

The air Squadrons went in force to their work, bent all their energies for the moment to the one great task of breaking up the masses before they could bring their weight into the line, of upsetting the careful time-table which the enemy must lay down and follow if they were to handle with any success the huge bulk of traffic they were putting on road and rail. Each Flight and Squadron had its own appointed work and place, its carefully detailed orders of how and where to go about their business. In one Squadron, where the C.O. held council with his Flight Leaders and explained the position and pointed out the plans, one of his Captains summed up the instructions in a sentence. "That bit of road," he said with his finger on the map, "you want us to see it's 'No Thoroughfare' for the Hun up to dark?"

"That's it," said the C.O. "And if you get a chance at a train or two about here—well, don't let it slip."

"Right-oh," "That's simple," "No Thoroughfare," said the Captains, and proceeded about their business. The Flights went off at short intervals, intervals calculated to "keep the pot a-boiling," as closely as possible, to allow no minutes when some of the Squadron would not be on or about the spot to enforce the "No Thoroughfare" rule. For the rest of the afternoon they came and went, and came and went, in a steady string, circling in and dropping to the 'drome to refill hurriedly with fresh stocks of bombs and ammunition, taking off and driving out to the east as soon as they had the tanks and drums filled and the bombs hitched on. They were on scout machines carrying four light bombs and many hundred rounds of ammunition a-piece, and Dennis, the leader of the first Flight, made an enthusiastic report of success on the first return. "Found the spot all right, Major," he said cheerfully. "The crater reported is there all right, and it has wrecked half the road. There was a working party on it going like steam to fill in the hole, we disturbed the party a whole lot."

They had disturbed them. The road was one of those long miles-straight main routes that run between the towns in that part of France. They were well filled with troops and transport over the first miles, but the Flight Leader followed instructions and let these go, knowing other Squadrons would be dealing with them in their own good time and way. "Although I wish they'd get busy and do it," as he told the C.O. "Having nothing to worry them, those Huns just naturally filled the air with lead as he went over 'em. Look at my poor old 'Little Indian' there; her planes are as full of holes as a sieve."

But he had pushed his "Little Indian" straight on without attempting to return the fire from below, and presently he came to the spot where the Squadron was to tackle its job—a spot where an attempt had been made by our Engineers to blow up the road as we retired, and where a yawning hole took up half the road, leaving one good lorry-width for the transport to crawl round. An infantry battalion was tramping past the crater when the Flight arrived above it, and since the "Little Indian" flew straight on without loosing off a bomb or a shot, the rest of the Flight followed obediently, although in some wonder as to whether the target was not being passed by mistake. There was no mistake. They followed the leader round in a wide sweep over the open fields with stray bunches of infantry firing wildly up at them, round to the crater, and past it again, and out and round still wider. The road by the crater was empty as they passed, but a long string of lorries and horse transport that had been waiting half a mile back began to move and crawl along towards the crater. The "Little Indian" kept on her wide circle until half the lorries were past the crater. Then she came round in a steep bank and shot straight as an arrow back to the road, swept round sharply again and went streaking along above it. Two hundred yards from the crater she lifted, curved over and came diving down, spitting fire and lead as she came, pelting a stream of bullets on the lorries abreast of the mine hole and diving straight at them. Thirty feet away from the hole, one, two, three, four black objects dropped away from under the machine, and four spurts of flame and smoke leaped and flashed amongst the lorries and about the hole, as the "Little Indian" zoomed up, ducked over and came diving down again with her machine-guns hailing bullets along the lorries and the horse transport. And close astern of her came the rest of the Flight, splashing their bombs down the length of the convoy, each saving one or two for the spot by the crater, continuing along the road and emptying their guns on the transport. Half a mile along the road they swung round and turned back and repeated the gunning performance on men struggling to hold and steady crazed and bolting horses, on wagons in the ditches, on one lorry with her nose well down in the half-filled crater and another one comfortably crashed against her tail that stuck out into the half-width bit of road.

"A beautiful block," the Flight told the Major on their return. "Couldn't have placed 'em better if we'd driven the lorries ourselves. And there's horse wagons enough scattered along the ditches of the next half mile to keep the Hun busy for hours."

The second Flight, arriving about ten minutes after the first had departed homeward bound, found the Huns exceedingly busy struggling to remove the wrecked transport which so effectually blocked the way. There were men enough crowded round the crater especially to make a very fine target, and the first machine or two got their bombs well home on these, and scattered the rest impartially along the road on any "suitable targets" of men or transport. They established another couple of very useful blocks along the mile of road behind the crater, and completely cleared the road of marching men for a good three miles. The third Flight found no targets beyond the working party at the crater until they had gone back a few miles to a cross road, where they distributed some bombs on a field battery, bolted the teams, and left the gunners well down in the ditches beside their overturned guns and limbers.

They had barely finished their performance when the first Flight was back again, but by this time the enemy had taken steps to upset the arrangements, and with a couple of machine-guns posted by the crater did their best to keep the traffic blockers out of reach of their targets. But the Flight would not be denied, and drove in through the storm of bullets, planted their bombs and gave the ground gunners a good peppering, and got away with no further damage than a lot of bullet holes in wings and fuselages. For the next hour the Germans fought to strengthen their anti-aircraft defences, bringing up more machine-guns and lining the ditches with riflemen, and the attackers got a reception that grew hotter and hotter with each attempt. But they held the road blocked, and effectually prevented any successful attempt to clear and use it, and in addition extended their attacks to further back and to other near-by roads, and to the railway. Crossing this line on one outward trip Dennis, still flying his bullet-riddled "Little Indian," saw a long and heavily-laden train toiling slowly towards the front. It was too good a chance to miss, so he swung and made for it, swooped down to within a hundred feet and dropped his bombs. Only one hit fairly, and although that blew one truck to pieces, it left it on the rails and the trains still crawling along. But the Flight followed his lead, and one of their bombs hit and so damaged the engine that a cloud of steam came pouring up from it and the train stopped. Another long train was panting up from the German rear, so the Flight swept along it and sprayed it liberally with machine-gun bullets, scaring the driver and fireman into leaping overboard, and bringing that train also to a standstill. Dennis headed back home to bring up a fresh stock of bombs, and, if he could, damage the train beyond possibility of moving, although he feared it was rather a large contract for a scout's light bombs. But on the way back he met a formation of big two-seater bombers carrying heavy bombs, and by firing a few rounds, diving athwart their course, and frantic wavings and pointings managed to induce them to follow him. Two of them did, and he led them straight back to the two trains. The driver and fireman of the second had resumed their duties and were trying to push the first train along when the bombers arrived, and planting one bomb fairly on the train, started a fire going, and with another which fell between two trucks blew them off the metals. The burning trucks were just beginning to blow up nicely as our machines raced for home and more ammunition.

The next hour was mainly occupied with a fast fight against about twenty Hun machines evidently brought up to break up the road-blockers' game. The fight ended with three of the Huns being left crashed on the ground, one of ours going down in flames, and two struggling back across the lines with damaged machine and engine. Dennis was forced to leave his machine for one trip and borrow another while his damaged wings were replaced with new ones.

This time two Flights went out together, and while one engaged the Hun machines which still strove to drive them back, the other dived back on the road and again scattered the working party which struggled to clear the road. They had a hot passage, whirling down through a perfect tempest of machine-gun fire, and another machine was lost to it. Dennis struggled back across the lines with a shot-through radiator and an engine seizing up, was forced to land as best he could, wrecked his machine in the landing, crawled out of the wreckage, got back to the 'drome, and taking over his repaired machine went out again.

"That road's blocked," he said firmly, "and she's goin' to stay blocked." And he got his men to rig a sort of banner of fabric attached to a long iron picket-pin harpoon arrangement, painted a sentence in German on it, and took it up with him. They found the road still blocked, but columns of troops tramping in streams over the fields to either side. They spent a full hour scattering these and chasing them all over the landscape, had to break off the game to take on another fight with a crowd of Hun scouts, were joined by a stray Flight or two who saw the fight and barged into it, and after a mixed fast and furious "dog-fight" at heights running from anything under 300 feet to about as many inches, chased the Hun machines off. They came back in triumph down the deserted road and the empty fields, spattering the last of their rounds into the wrecked lorries and wagons still lying there, and then, as they passed over the piled wreckage at the crater, Dennis leaned out and dropped his streamered harpoon overboard. It plunged straight, hit, and stuck neatly upright displaying its legend clearly to anyone on the ground.

"What was on it?" said Dennis in answer to the questions of the Flight later on. "It was a notice in German. Maybe it was bad German, but it was a dash good notice. It said 'No Thoroughfare,' and I fancy we've taught the Huns what it means anyhow."

They, and a good many of their fellow squadrons, had, on this and on other road and rail Lines of Communication. They lost men and they lost machines; but the expected fresh attack on the line did not develop at dusk as foretold.

And that night the weary troops slept a solid life-renewing six hours.