Halley's Comet helped to announce the fall of the Shang Dynasty in China, a solar eclipse frightened the Macedonian army enough at Pydna in 168 BC to ensure victory for the Romans, wind and disease conspired to wreck the Spanish Armada, and an earthquake helped to spark the Peloponnesian War. But as David Petriello explains here, over the past 4000 years, weather and nature have both hindered and helped various campaigns and battles, altering the course of history in the process. Today elements of nature still affect the planning and waging of war, even as we have tried to mitigate its impact, and Petriello shows how growing concern over climate change has only heightened the need to study and understand this subject.