Konrad Zacharias Lorenz was an Austrian zoologist, ethologist and ornithologist. He shared the 1973 Nobel Prize in Physiology or Medicine with Nikolaas Tinbergen and Karl von Frisch. He is often regarded as one of the founders of modern ethology, the study of animal behaviour. He developed an approach that began with an earlier generation, including his teacher Oskar Heinroth. Lorenz studied instinctive behaviour in animals, especially in greylag geese and jackdaws. Working with geese, he investigated the principle of imprinting. Although Lorenz did not discover the topic, he became widely known for his descriptions of imprinting as an instinctive bond. Lorenz's work was interrupted by the onset of World War II and in 1941 he was recruited into the German Army as a medic. In 1944, he was sent to the Eastern Front where he was captured by the Soviet Red Army and spent four years as a German Prisoner of War in Soviet Armenia. Lorenz wrote numerous books, some of which, such as King Solomon's Ring, On Aggression, and Man Meets Dog, became popular reading