In what year was World War II declared?
World War II was declared on September 1, 1939, when Germany invaded Poland. Many countries, including France and the United Kingdom, responded to the invasion by declaring war on Germany.
Complete the following task based on the instruction and optional input provided.### Instruction:
In what year was World War II declared?

### Output:
World War II was declared on September 1, 1939, when Germany invaded Poland. Many countries, including France and the United Kingdom, responded to the invasion by declaring war on Germany.