For many years the Rhineland area had been a key industrial region of Germany: producing coal, steel and iron resources.
The Rhineland also formed a natural barrier to its neighbour and rival, France. In the event of a war, the River Rhine, if properly defended, would be a difficult obstacle for an invading force to cross.
One of the terms of the Treaty of Versailles was that the Germans would not be able to keep military forces in a 50 km stretch of the Rhineland. Hitler resented this term as it made Germany vulnerable to invasion. He was determined to enlarge his military capability and strengthen his borders.
In 1935, Hitler revealed that he had built up an air force and signed the Anglo-German Naval Agreement that allowed him to enlarge his naval forces.
In 1936, Hitler boldly marched 22,000 German troops into the Rhineland, in a direct contravention of the Treaty of Versailles. Hitler offered France and Britain a 25 year non-aggression pact and claimed:
Germany had no territorial demands to make in Europe