Soldiers is a tactical, company-based, battalion level, game of warfare in the brief, mobile phase at the beginning of the First World War. This was the time before paralyzing trench lines had been dug and consolidated.
The original rules credit both Isby and Glynn as designers, but the errata indicates Isby was the designer, and Glynn was the developer. In Moves #4 Isby describes Dunnigan suggesting the design to him in the original S&T basement premises a good two years before the game was published, giving him an extended time (compared to the usual SPI schedule) to research, design and test his prototype. He was able to trial 40 scenario proposals before settling on the set provided. This helps explain why it is such a good polished game which still holds up; the recent S&T game First Blood, Second Marne by Ty Bomba draws heavily on it.