World War II began 70 years ago, Tuesday, with a German blitzkrieg across Poland. Leaders from both the Allies and the Axis gathered in Gdansk, Poland to mark the anniversary. 

The six-year war turned into the 20th century's bloodiest conflict, leaving more than 50 million people dead.
    
German Chancellor Angela Merkel spoke of the Holocaust.

"In remembrance I think of the six million Jews and all the others who met a gruesome death in German concentration and extermination camps," Merkel said. "I think of the many millions of people who lived through struggle and rose up against Germany.

"I think of all those who, innocent, had to die from hunger, the cold, and sickness due to the violence and consequences of the war," she continued. "I think of the 60 million people who lost their lives in this war, which was unleashed by Germany."

At its height, World War II not only involved almost all the nations of Europe, but America, Australia and all of Asia as well.