Debt of Honor is a techno-thriller by Tom Clancy, released on August 17, 1994, and a direct sequel to The Sum of All Fears. The plot follows Jack Ryan, who is pulled from retirement by President Roger Durling to become National Security Advisor, as a secret cabal of Japanese industrialists (the zaibatsu) seizes control of their government and wages war on the U.S. The conflict is triggered by a trade war stemming from faulty Japanese gas tanks, leading Japan to launch a devastating surprise attack that includes occupying the Mariana Islands, torpedoing the U.S. Pacific Fleet, and crashing the U.S. stock market with a computer logic bomb. Ryan counters by engineering a financial "do-over" to restore the market, while U.S. special forces and stealth aircraft (B-2s and F-22s) destroy Japan's hidden ICBMs and air defenses. The novel debuted at number one on The New York Times bestseller list and is famously noted for containing plot elements eerily similar to the September 11, 2001 attacks and the hijacking of United Airlines Flight 93.