Removing the Guard is an important tactic. Attack the piece that defends another one that you would like to attack, and often you can win one of the two. This position is number 475 in Fred Reinfeld, 1001 Winning Chess Sacrifices and Combinations. This book is readily available for about $10 at many bookstores, but in order to read the solutions, you need to understand descriptive notation. Reinfeld explains descriptive notation in the front of the book. Many chess masters started with this book as their first text for tactics training. Computers dominate most players' training regimen today, but even Reinfeld's book has not outlived its usefulness. See "Where the Rubber Meets the Road" for a suggestion of how this book is useful in computer training.
Scholastic players and parents: The label "Problem of the Week" links to posts that contain my "lesson of the week." These blog posts serve to reinforce what is presented in my after school and in-school chess clubs.
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