Ruy Lopez Ajedrez", written in 1561. Although it bears his name, this particular opening was included in the Göttingen manuscript, which dates from c. 1490. However, popular use of the Ruy Lopez opening did not develop until the mid-19th century, when Carl Jaenisch, a Russian theoretician, "rediscovered" its potential. The opening remains the most commonly used amongst the open games in master play; it has been adopted by almost all players during their careers, many of whom have played it with both colours. Due to the difficulty for Black in achieving equality, a common nickname for the opening is "The Spanish Torture".
Tactical decision game consisted of scenarios that described situations faced by the commanders of battalions, companies, and platoons. In 1982, the Education Center of the United States Marine Corps Development and Education Command used this package as the starting point for a series of three "instructional pamphlets": "Tactical Problems for Battalion Commanders", "Tactical Problems for Platoon Leaders/Company Commanders", and "Tactical Problems for Squad Leaders". In addition to twelve problems taken from "What Now, Lieutenant?", the "Tactical Problems ..." series contained sixteen games that were written expressly for the series by Chief Warrant Officer Bryan N. Lavender, USMC. Like the scenarios in "What Now,