The British army swelled in size at the beginning of World War I. But many of these new recruits suffered from malnutrition and lacked the physical strength to serve on the front line. Doctors developed healthy diets and workouts for the soldiers and, within months, the army was ready to fight.

Biology has always been an important part of war. Doctors use biology to keep troops healthy by treating wounds and effects of trauma. Biologists have developed weapons that use germs to spread deadly diseases. Warfare has led to incredible advances in biology and medicine. From blood transfusions to biological weapons, learn how doctors and biologists have changed the face of warfare