The forbidding snow-covered Hindu Kush mountains of Afghanistan and Pakistan have long protected the Indian subcontinent from invaders. But they couldn’t stop Alexander the Great, who in 327 B.C. swept through the plains of Bactria into the Punjab, where he tangled with a mighty rajah. Author Frank Holt recounts this saga in “Alexander in the East,” and Rekha Morris tells how eastern artists began “Imagining Buddha” in great works of sculpture by drawing on Alexander’s legacy.