Chess opening are so complex and theoretical that amateur players will have trouble understanding them. An example is the Perenyi Attack of the Sicilian Defense (see diagram) which yields an immensely complicated and tactical position that even strong players have difficulty handling, and that is beyond the comprehension of most amateurs. Major changes in the rules of chess in the late fifteenth century increased the speed of the game, consequently emphasizing the importance of opening study. Thus, early chess books, such as the 1497 text of Luis Ramirez de Lucena, present opening analysis, as does Pedro Damiano (1512), and Ruy López de
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,