With the outbreak of World War II, doctors and nurses patriotically volunteered to serve. The Clinic’s Naval Reserve Unit was called to active duty. It included some of the Clinic’s most prominent physicians, including Dr. Crile’s son, George Crile Jr. A year after the war’s end, the Clinic’s six original departments had increased to 19 clinical departments. Work began on the vertical expansion of what is now the S building and two new hospital wings. With the arrival of Dr. Irvine Page as Head of Research, Cleveland Clinic was catapulted to the forefront of hypertension research.