Santiago Ramón y Cajal entered the Medical Corps after graduating in Medicine in 1873. His marked Spanish nationalist character and his excellent physical condition led him to serve in the third Carlist war as a medical lieutenant and later in the Cuban War as a captain. His stay in Cuba, however, was marked by hardship and illness. The decline of Spain’s colonialist policy, the war that was fought in a hostile climate and atmosphere, and the corruption of the military officers led to Santiago being posted to the frontlines on a fixed logistics system of trails. All this was to end in military failure and the subsequent loss of the colony. Disillusioned and seriously ill from malaria, which nearly killed him, he returned to Spain after being discharged for illness. Shortly afterwards, thanks to Dr. Jenaro Casas, he became a university lecturer, which put an end to his military career

Santiago Ramón y Cajal opositó a Sanidad Militar tras finalizar su licenciatura de Medicina en 1873. Su carácter marcadamente españolista y su excelente forma física le hicieron participar en la tercera guerra carlista con el empleo de teniente médico, y en la guerra de Cuba con el de capitán. Sin embargo, su estancia en Cuba estuvo marcada por las penalidades y la enfermedad. El declive de la política colonialista de España, la guerra en un clima y ambiente hostiles y la corrupción de los mandos militares hicieron que Santiago estuviera destinado en pleno teatro de operaciones dentro de un rígido sistema logístico de ‘trochas’, que acabaría en un fracaso militar y a la posterior pérdida de la colonia. Desencantado y gravemente enfermo de malaria, que estuvo a punto de causarle la muerte, regresó a España con licencia por enfermedad. Poco después ingresó como docente universitario de la mano del Dr. Jenaro Casas, lo cual supuso el fin de su carrera castrense.