Excerpt from The Volunteer by Jack Fairweather, plus links to reviews, author biography & more

His instincts told him to lie perfectly still but it was an agony to listen to the shrieks and groans of his men being massacred. Eventually the guns fell quiet and he slipped away from the carnage and found a dozen survivors and horses in the dark fields beyond the town. The assault had lasted only a few minutes, but he'd lost most of his men; dead or injured or captured, he didn't know. He hoped the Polish line had held more resolutely elsewhere. Witold made for Warsaw with the other survivors, knowing that all would be lost if they couldn't hold the capital.

At first they seemed to be behind the front line. Following Hitler's edict to destroy the Poles, the German military bombed and strafed fleeing civilians, and corpses littered the roadside beside carts piled high with luggage and furniture. But as they neared Warsaw the following day the roads started to fill with the living, and Witold realized he'd overtaken the Germans. The crowds of men shouldering bundles or herding livestock and women dragging children looked nervously to the sky.

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Witold rode into Warsaw on the evening of September 6. He had no radio and no way of knowing the scale of the disaster that had unfolded elsewhere: the Germans had broken through Polish lines at multiple points and were moving rapidly to encircle Warsaw. Advance units were expected at any moment. Britain and France had declared war on Germany, but there was no sign of action. The Polish government had already fled, and the British delegation in the city was preparing to.

"Inside the Embassy, cases of the Ambassador's wine lay abandoned in the hall, his butler was in tears and the steps were littered with all sorts of personal kit, including an immaculate pair of polo boots," recalled Peter Wilkinson, one of the delegation members, who made sure the embassy's excellent wine cellar got loaded onto their five-ton truck before departure.

The only defenses Witold saw, riding toward the city center, were a couple of overturned tram cars that served as a barricade. Residents ran past layered in what looked like their entire wardrobe or kitted out as if for the ski slopes in garish pants and bandanas. Soldiers straight from the front were slumped on the pavements. Just the look of them, weary and disinterested, was enough to know what had happened. Even the air raid sirens had ceased to sound. Stopping to ask one man in a hunting cap and smoking a cigar for directions, Witold was answered in German with a smirk. He was a member of the country's sizable ethnic German population that the Nazi leadership was urging to turn on its Polish neighbors. Incensed, Witold struck him across his face with the flat of his saber and rode off.

Witold finally located Warsaw's military headquarters on Krakowskie Przedmieście Street near the royal castle, where he learned that there was a plan to defend the city and enlist the help of civilians in building barricades and preparing for a siege. Witold was given oats and hay for his horse, but he had no clear instructions on which unit to join or what to do. He decided that they'd be better off falling back and joining whatever Polish forces were regrouping in the east to launch a counterstrike. On September 9, with the Germans' encirclement almost complete, Witold and his men slipped away to the city of Łuków, fifty miles southeast of Warsaw, where he was told he could find the Polish military's overall command. By the time Witold arrived, the small city had been bombed and reduced to smoking ruins. A peasant woman lay beside one crater, her skirts blown over her head to expose her pale white thighs, a mangled horse beside her.

In Łuków, he was told that the commanders had retreated to the next town, but when he got there it was the same story. And so it went in place after place, bombed and abandoned. The German strategy was to strike towns and infrastructure far in advance of its ground troops to prevent the Poles from regrouping. Even the train station in Witold's distant hometown, Lida, was attacked. The roads were jammed with civilians and soldiers pursued and harried by dive bombers as they moved east. "We are now no longer an army, a detachment, or a battery," recalled one soldier, "but individuals wandering collectively towards some wholly indefinite goal."

Excerpted from The Volunteer by Jack Fairweather. Copyright © 2019 by Jack Fairweather. Excerpted by permission of Custom House. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.