Pliny the Elder (born Gaius Plinius Secundus, AD 23 – 79) was a Roman author, naturalist and natural philosopher, a naval and army commander of the early Roman Empire, and friend of the emperor Vespasian. Spending most of his spare time studying, writing, and investigating natural and geographic phenomena in the field, Pliny wrote the encyclopedic Naturalis Historia (Natural History), which became an editorial model for encyclopedias. Pliny the Younger refers to Tacitus’s reliance upon his uncle's book, the History of the German Wars. Pliny the Elder died in AD 79, while attempting the rescue, by ship, of a friend and his family, in Stabiae, from the eruption of Mount Vesuvius, which already had destroyed the cities of Pompeii and Herculaneum. The wind caused by the sixth and largest pyroclastic surge of the volcano’s eruption did not allow his ship to leave port, and Pliny probably died during that event.