Poland.
Germany invaded Poland
They invaded Poland.
Poland
Nazi Germany and the USSR invaded Poland in 1939.
Poland was invaded by Germany in 1939 that started World War II.
Hitler's invasion of Poland on september1 1939 triggered WWII
They were invaded in 1939.
I dont think any country in 1993. perhaps you meant 1939, which was Germany?
1939
World War II began on September 1, 1939 when Germany invaded Poland.
When Hitler invaded Poland in September 1939