An in-depth history of the attack that began World War II, and one country's courageous fight against two unstoppable forces.   Hitler's military offensive against Poland on September 1, 1939 was the brutal act that triggered the start of World War II, wreaking six years of death and bloodshed around the world. But the campaign is often overshadowed by the momentous struggle that followed across the rest of Europe.   In this thought-provoking study, each stage of the battle is reconstructed in graphic detail. The author examines the precarious situation Poland was in, caught between Nazi Germany and the Soviet Union. He also reconsiders the pre-war policies of the other European powers--particularly France and Britain--and assesses the evolving scenario in a vivid, fast-moving narrative.   Included throughout are first-hand accounts of soldiers and civilians who were caught up in the war as well as the Polish capitulation and its tragic aftermath.