It has been more than 20 years since the United States and coalition forces entered Kuwait and Iraq. Actual combat was of remarkably short duration: less than 1 week of sustained ground activity and 6 weeks of air missions. Thus, it was surprising when approximately 200,000 returning US veterans were affected by a chronic multi-symptom illness that came to be known as Gulf War Illness (GWI). There were many challenges in investigating GWI, not least of which was that it took several years before the condition was officially taken seriously. There were multiple exposures to potentially causal agents on and off the battlefield, but these exposures were documented incompletely if at all, leaving epidemiologists to rely on self-report for information. In the past 2 years, significant controversy has arisen over the future directions of the field. Despite these challenges, several studies have implicated exposure to acetylcholinesterase inhibitors such as pyridostigmine bromide in the genesis of the condition. The story of GWI can inform research into other conditions and guide future work on veterans' health.