Sam Kean - 9 July

As the soldiers darted out of the cottage, the doorframe near their skulls exploded in splinters. This wasnt the first time someone had shot at Boris Pash that day, and it wouldnt be the last. An hour earlier Pash and a lieutenant had crept into the booby-trapped forest surrounding this seaside cottage in northern France. Seven brave resistance fighters had already died in these woods, but Pash had a swashbucklingsome said recklessstreak and had plunged ahead anyway. His mission: to capture a local scientist. As for why he needed to capture him, Pash was keeping mum. But echoing through his mind that day were the last words hed heard from his bosses in Washington a few weeks earlier: Any slight delay in reaching your targets might cost us tremendous losses, or even the war.

This wasnt an exaggeration. Pash led a team of scientific commandos called the Alsos Unit, who roamed around Europe collecting secrets about the most dreadful threat they could imagine: the Nazi atomic bomb project. Because Alsos (all-soss) worked independently, unattached to any larger military group, people called it the Bastard Unit. But the nickname was equally apt for Pash himself, a hard-charging World War I veteran whose unruliness behind enemy lines gave his minders back in Washington gastric ulcers.

At the same time, the desk jockeys needed a bastard like Pash: he took on missions no one else could or would. Like hunting down a scientist in a seaside village in France that was still under Nazi control. The man in question was a Nobel Prizewinning physicist rumored to be collaborating with the Germans on nuclear research. His capture could therefore disrupt the entire Nazi bomb project and keep atomic weapons out of Adolf Hitlers hands.

But after slinking past all the pressure mines and tripwires in the forest, Pash and his sidekick had arrived at the cottage to find something sickening: nothing. The door was ajar and the cottage abandoned, stripped bare and full of debris. They searched everywhere, but there were no documents, no equipment, and certainly no nuclear scientist. Washington had feared that even a slight delay in finding the target could cost the Allies the war. Now the target had vanished. A dejected Pash and his lieutenant made ready to leave. At which point bullets splintered the doorframe near their heads. Then came the machine-gun fire.

Both men dived to the dirt outside and began belly-crawling into the cover of the woods. Given the secret nature of his mission, Pash had told very few people what they were up to that day. He therefore had no idea who was firing at them or whyNazis, Americans, French renegades of dubious loyalty. Whoever it was had one clear objective: to make Pash and his sidekick the eighth and ninth casualties in the hunt for the French nuclear physicist.

Meanwhile, as Boris Pash was dodging gunfire, the Bastard Units new scientific chief was weathering a calamity of his own. Samuel Goudsmit, a soft and somewhat dandyish nuclear physicist, had arrived in London shortly after D-Day, just in time to see the first V-1 rockets smash down. In the dead of night, people in the city would hear a buzzing noise in the dark above them, until the rockets motor cut and it began to plunge. Several seconds of dreadful silence followed; many held their breaths until the