The Soviet Union, or USSR.
Belgium
France
They invaded Poland.
Germany invaded France and Poland also it invaded Austria. World War 2 started because Germany said to England they wouldn't invade Poland but they did - so Poland is the easiest country to remember that was invaded!
Germany
Germany invaded Poland
Germany invaded France
The Soviet Union, or USSR.
Germany
poland
Switzerland
Germany from the west and USSR from the east.
Belgium
Germany invaded Poland.
Germany invaded Poland and as a result France and England declared war on Germany.
Poland was invaded by Germany just before the war was declared.