In 1939 Levi began his love affair with hiking in the mountains. A friend, Sandro Delmastro, taught him how to hike, and they spent many weekends in the mountains above Turin. Physical exertion, the risk, and the battle with the elements while following Sandro's example enabled him to put out of his mind the nightmare situation precipitating all over Europe as, communing with the sky and earth, he managed to satisfy his desire for liberty realize fully his own strength, and the reasons behind his ardent need grasp the nature of things that had led him to study chemistry, as he later wrote in the chapter "Iron" of "The Periodic Table" (1975). In June 1940 Italy declared war as an ally of Germany against Britain and France, and the first Allied air raids on Turin began two days later. Levi's studies continued during the bombardments. The family suffered additional strain as his father became bedridden with bowel cancer.