Ruy Lopez that after the common retreat 4.Ba4, Black will have the possibility of breaking a future pin on his by playing ...b5. White must take some care not to fall into the Ruy Lopez, Noah's Ark Trap, in which Black traps White's on the b3-square with a ...a6, ...b5, and ...c4 pawn advance on the . Ercole del Rio, in his 1750 treatise "Sopra il giuoco degli Scacchi, Osservazioni pratiche dell'anonimo Modenese" (On the game of Chess, practical Observations by an anonymous Modenese), was the first author to mention 3...a6. However, the move became popular after it was played by Paul
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,