Simeon Thayer fought in Rogers' Rangers during the French and Indian War and made a harrowing escape from French-allied Indians. At the outbreak of the American Revolutionary War, the Rhode Island assembly appointed him an officer. He quickly raised a company of soldiers and marched with them to the Siege of Boston. He and his men went on Benedict Arnold's expedition to Quebec during which time he kept a journal of his experiences. He fought at Quebec and was captured. After being paroled, he again served as an officer in the Continental Army. Simeon Thayer was a member of the Society of the Cincinnati of the State of Rhode Island.

Rogers' Rangers was a company of soldiers from the Province of New Hampshire raised by Major Robert Rogers and attached to the British Army during the Seven Years' War. The unit was quickly adopted into the British army as an independent ranger company. Robert Rogers trained and commanded the rapidly deployed light infantry force, which was tasked mainly with reconnaissance as well as conducting special operations against distant targets. Their tactics were built on earlier colonial precedents and were codified for the first time by Rogers as his 28 "Rules of Ranging". The tactics proved remarkably effective, so much so that the initial company was expanded into a ranging corps of more than a dozen companies. The ranger corps became the chief scouting arm of British Crown forces by the late 1750s. The British forces in America valued Rogers' Rangers for their ability to gather intelligence about the enemy. They were disbanded in 1761.