The 50th anniversary of the Korean war saw another mystery of that area revealed. How were the North Korean's able to achieve such complete surprise when they attacked South Korea? Simple. Stupidity and laziness on the part of US intelligence agencies. Even though we had cracked Russian codes right after World War II, a Russian immigrant, serving in the US army, but actually a KGB spy, let Soviets know, and codes were changed in 1948. This Soviet agent was under suspicion for several years before he did the damage, but the matter was never pursued vigorously. Despite that, the US still had numerous other sources of information on Russia and North Korea. But signs, like massive shipment of military medical supplies to North Korea, were ignored. Even after the war began, evidence of massive Chinese troop movements into North Korea were dismissed as a feint.