by Close, Frank
Thus, the fission of natural rocks is rare because they contain so little U-235. While that is good news for our daily affairs, it makes it difficult to extract nuclear energy from raw uranium. To do so effectively one must first increase the amount of U-235 in the target, a process known as enrichment. This is difficult but, as would soon become clear, not impossible. Bohr published his insight in Physical Review in September 1939. It is ironic that the means that would help bring World War II to a close made its debut in the same week that the war in Europe began.
By January 1940 the French team had decided that heavy water was the best means to moderate the neutrons, as the first step toward unlocking nuclear energy from uranium. Frédéric Joliot-Curie alerted the French Minister of Supply that uranium could be the key to abundant energy or to a weapon of immense power. Also, he emphasized the special role that heavy water could play. The only European producer of heavy water in large amounts was the Norsk Hydro electric company in Norway; Frédéric explained that they would need “the whole of this stock.”67
Then the team had a lucky break. On February 20, they learned that one of the minister’s military contacts, Jacques Allier, had been a banker before being called up. The good fortune was that Allier’s bank was the majority stakeholder in the Norwegian factory.
Allier, accompanied by some members of the French secret service, went to Norway and explained the situation. They stressed to the Norwegians that it was essential to “rescue” the entire stock of heavy water before the Germans invaded Norway. The Norwegian government feared a German invasion and was trying to appear neutral, even though its sympathies were transparent.
The French delegation was successful. In the second week of March 1940, the scientists received a telegram with the heading “absolute secrecy.” It summoned them to a meeting where they learned that the entire stock of heavy water—some forty gallons—had arrived. At last they could plan experiments to determine the necessary conditions for a chain reaction.
Within weeks, the Germans invaded France and entered Paris. Kowarski and Halban set out on an odyssey, escaping to England with the heavy water to keep it out of Nazi hands. If Joliot-Curie had gotten his wish, Pontecorvo would have been with them, but the British authorities vetoed this plan. When British security viewed Frédéric’s list of scientists, it gave the following assessment: “Dr PONTECORVO, a collaborator of Professor JOLIOT, is regarded as ‘mildly’ undesirable: might possibly be allowed to work if vital to the war effort, but even if working should be watched.” There was no reason given for their description of Bruno as “undesirable.”68 In any event, Bruno had to make other arrangements.
The precious liquid would eventually end up in Canada, where, by a sequence of coincidences, Halban and Kowarski would be reunited with Pontecorvo. After the invasion, Joliot-Curie remained in Paris, where he became active in the French Resistance. Pontecorvo, being a Jew, was a target for the Nazis, and, as an Italian in France, he was an enemy alien. The options he’d laid out in his manifesto, which Marianne had agreed to, had now crystallized. Fascism had come to France; it was time to escape to the United States.
FOUR
THE FIRST ESCAPE
1940
ON THE MOONLIT NIGHT OF MAY 10, 1940, GERMAN TANKS BREACHED the Maginot Line; the Nazi army invaded France. The French tried to mount a defense along the Somme and Aisne Rivers in the north, but failed and withdrew to the Loire, south of Paris. Within two weeks the Allies had sacrificed northern France in service of a greater strategy: “He who fights and runs away lives to fight another day.” A desperate evacuation of British troops from Dunkirk began on May 27, and was completed by June 4.
In April, while still in Paris, Halban and Kowarski had made a few preliminary measurements using the heavy water. But as events began to unfold, and the German army approached, urgency turned to panic. On May 16, Raoul Dautry, the Minister of Armaments, phoned Joliot-Curie and urged him to transfer his project out of Paris.1 In the belief that the Loire would act as a southern limit to the German advance, they decided that Halban and an assistant would go to Clermont-Ferrand, about 260 miles south of Paris, and rent a villa, which could be used as an emergency laboratory. Kowarski and the heavy water would then join them there.
Hundreds of thousands of refugees began to flee south from Paris and its environs. In the midst of the mayhem, Bruno met with a tense and anxious Frédéric Joliot-Curie. Frédéric was a French patriot and decided to remain in the country. He urged Bruno to leave, however, adding, “It is best that you do so very soon.”2 Joliot-Curie understood the awful conundrum of Bruno’s position. As an Italian, he was now technically an enemy of France; as a Jew, he was no ally of the Nazis.
At this juncture, Bruno experienced a piece of good fortune, thanks to Emilio Segrè, his old physics colleague. Segrè had gone to Berkeley on a summer visit in 1938. While he was there, Mussolini had passed the anti-Semitic laws, which barred Jews from university posts in Italy. Segrè was Jewish, and, having become excluded from work in Italy, he remained in Berkeley. One day in 1939 he attended a meeting of European émigrés living in California, where he met two other migrants—nuclear physicists who were prospecting for oil, and on the lookout for a neutron expert.3 Segrè appeared to be manna from heaven. The physicists invited him to visit their laboratory in Tulsa, Oklahoma. In May 1940 he did so, but they were unable to tempt him to join them permanently; Tulsa was no competition for Berkeley, where Lawrence had built his cutting-edge cyclotron, and Segrè could watch the sun set behind the Golden Gate Bridge, across San Francisco Bay. Segrè turned their offer down, but, in doing so, he recommended Pontecorvo.4
Segrè wrote to Bruno, saying, “There is a good chance I can get you a job.” Thus it came to pass that, in the spring of 1940, Pontecorvo had an offer of employment in the United States, just days before the Nazis occupied Paris.
Bruno had already escaped fascism once, when he left Italy in 1936. Now, with his family in tow, he did so again. Bruno’s sister Giuliana, and her husband, Duccio Tabet, had also quit Italy, in 1938, and had rented a house in Toulouse.5 They had told Bruno, Gillo, and their cousin Emilio Sereni that if ever the occasion arose, they could regard the house as their home. That moment had arrived.
On May 24, Marianne and Gil received papers of safe-conduct, which allowed them to make a single journey by train, or as passengers in a car, to Toulouse. The documents were valid for three days, starting on June 2.6
Marianne, loaded with baggage, and Gil, deeply upset but too young to understand the crisis, crammed onto the train to Toulouse. When they arrived there, Duccio Tabet immediately drafted a written declaration that Marianne and Gil were guests in his house, at 16 rue Edouard Baudrimont. The Toulouse police approved this arrangement on June 7.7 Meanwhile, Bruno remained in Paris.
IMAGE 4.1. Safe-conduct document allowing Marianne and Gil to travel to Toulouse in 1940. (AUTHOR, CHURCHILL ARCHIVES CENTRE.)
THE START OF JUNE WAS HOT. THE SUN SHONE FROM A CLOUDLESS SKY.8 Even the nights were warm; stars twinkled in the crystal clear air. Two miles above the city, a German pilot could see twelve boulevards radiating from the Arc de Triomphe, as if it were at the center of a clock face. The Seine meandered through the suburbs, and separated in two to embrace the Île de la Cité at the city’s heart, where stood Notre Dame, which had survived centuries of history and revolution. To the immediate south of the cathedral, the narrow streets of the Left Bank were laid out like a map. That is where Bruno Pontecorvo suddenly awoke, on the night of Monday, June 3, as the German aircraft released its bombs.
Also in Paris were Bruno’s brother Gillo, their cousin Emilio Sereni, and Gillo’s French girlfriend, Henrietta. Bruno’s friend Salvador Luria, an Italian research colleague at the Radium Institute and a Sephardic Jew, was also worried about the Nazi advance.9 Among others for whom that night would frame the rest of their lives was Irène Némirovsky, a Jewish writer. She depicted the events in her novel Suite Française. Some of her characte
rs, such as the members of the Péricand family, started to evacuate immediately. Others, like the Michauds, hesitated until it was almost too late, even giving their apartment a final clean before they departed forever, naively dreaming that they would return someday. Her fictional refugees portrayed in microcosm the experiences of a million real ones, including the Pontecorvos, Sereni, and Luria.
Just before dawn on Tuesday, June 4, air-raid sirens sounded and the exodus began. During the final days of May, Kowarski had cleared out the laboratory he’d shared with Halban and prepared to move everything to Clermont-Ferrand, where he would join his colleague. In addition to the heavy water, he had to gather electronic amplifiers, radiation detectors, and a precious sample of radium and beryllium, which would provide their neutrons. The biggest task was moving several tons of lead bricks, used as radiation shields in the experiments.
By the fifth or sixth of June, Kowarski had loaded all of the lead, along with the rest of the equipment, onto several army trucks.10 Then, accompanied by half a dozen soldiers, the entire caravan joined the tide of humanity headed south from Paris, away from the Nazi army. Kowarski’s convoy reached Clermont-Ferrand on Friday the seventh; for security purposes he stored the heavy water in the nearby women’s prison, in Riom. His wife and child managed to join him by train a few days later.
BY THAT WEEKEND THE MAIN STREETS OF PARIS WERE ALMOST EMPTY. Metallic shutters covered the windows of shops, abandoned by their owners, who had joined the throng of refugees. However, some still believed that the flight was the result of “hysterical rumors” circulated by “traitors.”
Any doubts were removed on June 9, when the Germans assaulted the city. All major monuments were surrounded with sandbags; windows rattled, and “from the top of every monument birds rose into the sky” as the sounds of gunfire thundered across the rooftops.11 “The Germans have crossed the Seine . . . even animals can sense the danger,” declared one of Némirovsky’s anxious refugees, whose husband still seemed in a state of denial. Gillo Pontecorvo vividly recalled that someone in the street shouted, “The Germans are at Pontoise”—about 15 miles northwest of the center of Paris.12
The attack on the city and the rupture of the French defenses were so rapid that many were caught unprepared. For anyone with special reason to fear life under Nazi rule, the time had come to flee by any means possible: train, car, truck, or bicycle.
Frightened hordes descended on the railway stations. Their plans to escape were frustrated, however, when they found the platforms closed, guarded by soldiers. Would-be fugitives flooded the surrounding streets and offered taxi drivers small fortunes to take them out of the city. Money had ceased to have meaning; people, not possessions, were what mattered. But the taxis didn’t have enough gas to reach even the relative sanctuary of Orléans, about 70 miles to the south. Those without train permits or gasoline, which was almost everyone, set off on foot. The roads south of Paris were clogged, as up to a million refugees dragged their luggage behind them, or humped it in wheelbarrows and carts.
These were the last days of freedom in Paris. As the crescent moon rose, the clear night sky was suddenly obscured. What at first appeared to be storm clouds was actually a smoke screen, put up deliberately to save the city from being bombed.13 On Thursday the thirteenth, Paris was declared an open city, as the French government fled to Bordeaux. At this eleventh hour, Bruno, Gillo, Henrietta, and Emilio Sereni, along with Salvador Luria, joined the exodus—on bicycles. They were almost too late. The next day, June 14, the German army entered Paris.
AFTER SO MANY CLEAR, HOT DAYS, THE WEATHER BROKE ON JUNE 13. The rain showers may help explain the apparently casual nature of the group’s departure; having cycled hardly more than a mile, they stopped to say farewell to friends on the rue Mouffetard.14 These acquaintances could have been models for the Michaud family, who delayed until it was almost too late, or they might have been among those who were brave or foolish enough to remain and take their chances with the occupation. In any event, they insisted that the travelers stay a while and have something to eat.
Gillo, just twenty years old, and his girlfriend, Henrietta, seemed to regard the whole enterprise as a diversion, a frisson of excitement in the life of a self-confessed playboy. Their carefree attitude infected Bruno, who helped himself to two cream macaroons. Salvador Luria, a year older than Bruno and seemingly more aware of the seriousness of the situation, was shocked at his companions’ casual attitude. They had wasted precious time and he urged them to leave. By nightfall they reached a guesthouse about forty-five miles south of the city limits.
The next morning, when Gillo opened the bedroom window, he discovered that the square below was full of German tanks. The previous day’s carefree adventure was replaced by panic. He thought that further flight was pointless and that it would be better to return to Paris. However, Henrietta convinced him to continue the journey with the others. “Henrietta wanted to carry on south,” he later explained. “And so we did.”15
Whereas the day before they had been part of a steady exodus, now the streets were crowded and disorderly. People, desperate to escape, lined the roadside in the hope of finding some form of transportation. Thousands of cars littered the shoulders, broken down or out of gas. Streams of refugees and army vehicles were on the move. The main line of cars, their roofs piled high with suitcases, crowned with mattresses, looked like unstable piles of bric-a-brac on wheels. A procession of cars, vans, trucks, tractors, anything with four wheels, lumbered along in single file. The vehicles, which crept forward like snails, obstructed the torrent of pedestrians and horse-drawn wagons. In turn, the crush of refugees traveling on foot, meandering around and between the vehicles, blocked the roads and interfered with oncoming traffic.
Like a scene from a film noir, this mayhem formed the backdrop as Gillo and Henrietta, clad in shorts and carrying skis, cycled past on a tandem, along with Bruno, Sereni, and Luria. Someone shouted contemptuously, “Look at those bourgeois, going on holiday!”16
Up to that point their travels had indeed been like a vacation, in that they had stayed overnight at a hostel. Now everything abruptly changed. At Orléans and beyond, there wasn’t a single bed free. People slept—or at least tried to—in their cars, in shop doorways, or even on the sidewalk, using suitcases as pillows. Sonia Tamara, a correspondent for the New York Herald Tribune, was in Orléans a day before the Pontecorvo party, and recalled that the scene near the railway station was “appalling.” People lay on the floors inside, and filled the town square outside. Children were crying, and there was nothing to eat in the entire town.17
Refugees were everywhere. Some, like the Pontecorvos, had a specific destination in mind. Others just wanted to get away. No one knew where or when the Germans would appear to cut off their escape. The choice of the best route was a lottery. Many roads were closed, which forced refugees to take detours as soldiers and police made desperate attempts to let army vehicles through. Piles of stones and bricks blocked the outskirts of every village. In revolutionary tradition, peasants manned these makeshift barricades and examined the papers of the fugitives.
Yet in the midst of this mayhem the postal service appears to have kept functioning, at least in the south, away from Paris. For on June 14 Bruno wrote a postcard to Marianne, which reached her in Toulouse.18 It would seem that by that evening the group had reached Beaugency, about ten miles south of Orléans and eighty from Paris, as it was there that he had time to write the postcard. It began, “J’ai quitté Paris depuis deux jours en vélo.” He continued, “I hope to get a train at Blois or some other place. If I can’t I shall come to Toulouse by bike but I don’t know when [I will arrive]. In Paris I didn’t receive any letter from you but I understand the post is not operating [there] anymore. The Hotel Grands Hommes was closed as I was leaving. I can tell you more when I arrive.”
On the morning of the fifteenth, the group set off once more toward Blois, thirty miles to the south. Their hopes of finding a train there were das
hed, however, and by nightfall they had progressed to Vierzon, south of Blois. They had logged a total of about fifty miles for the day, and 130 in all from Paris. That evening, Bruno mailed the postcard to Marianne from Vierzon. There were still nearly three hundred miles to go.
Emilio Sereni decided to travel by trails and minor roads, which he felt would be more secure. The Pontecorvos decided to take their chances with the shortest, fastest route. They reached Toulouse in about ten days; Sereni took a few days longer. At some point Salvador Luria left his friends and joined a different group of refugees, eventually reaching Marseilles. He later made it to the United States, and in 1969 won the Nobel Prize in Physiology or Medicine for his work on the genetic structures and reproduction of viruses.19
FRANCE SURRENDERS
Halban, Kowarski, and the precious heavy water, meanwhile, had arrived safely in Clermont-Ferrand. However, by the time Bruno started his odyssey southward, the plans of his former colleagues had been thrown into disarray.
On June 16, the prime minister resigned, to be succeeded by Marshal Philippe Pétain, who negotiated an armistice. This was signed on June 22. In 1918, Germany had formally surrendered to its World War I enemies in a railway carriage. In 1940, Germany’s revenge (and France’s humiliation) was completed when the French surrendered to Hitler in the very same carriage, at the very same spot. Germany now occupied the north and west of France. The south, which included Toulouse and Marseilles, was nominally independent. Pétain took charge of this area.
On the day of the prime minister’s resignation, Joliot-Curie had arrived in Clermont-Ferrand, in the independent south. He explained to Halban and Kowarski that, in his opinion, and that of government officials, France would remain divided for a period, but eventually the Germans would occupy the whole of the country. The plans for fission experiments at Clermont-Ferrand were therefore in jeopardy. Halban and Kowarski were ordered to go to Bordeaux at dawn the next day, June 17, along with the heavy water. Once there, they would receive further instructions.