The Fifth-Dimension Tube by Murray Leinster

The city was pandemonium. Tommy, looking down from his post of command, swore softly under his breath. The Death Mist was harmless to the defenders of Yugna as a gas, because of their gas masks. But it served as a screen. It blotted out the waves of attackers so the steam guns could not be aimed save at the shortest of short ranges. His precautions were taking effect, to be sure. Two thirds of the attackers were Ragged Men drawn from about half the surviving cities, and against such a horde Yugna could not have held out at all but for his preparations. Now the defenders took a heavy toll. Swarms of men came racing toward the open gate, their truncheons aglow in the sunlight. The ring of Death Mist was contracting as if to strangle the city, and it left the ramparts bare again. And from more than one point upon the battlements the roaring clouds of steam burst out again. A dozen guns concentrated on the racing men of Rahn, plunging from the jungle to enter by the gate. They were racing forward, without order but at top speed, to share in the fighting and loot. Then streams of metal balls tore into them. The front of the irregular column was wiped out utterly. Wide swathes were cut in the rest. The survivors ran wildly forward over a litter of dead and dying men. Electric-charge weapons sent crackling discharges among them. Their contorted figures reeled and fell or leaped convulsively to lie forever still where they struck. And then the steam guns turned about to fire into the rear of the men who had charged past them.

The steam guns had literally blasted away the line of Ragged Men where they stood. But the line went on, with great ragged gaps in it, to be sure, but still vastly outnumbering the defenders of the city. Here and there a steam gun was silent, its gun crew dead. And presently those that were left were useless, immobile upon the ramparts in the rear of the attack.