Watch Modern Marvels Season 7 Episode 24 Online

The Maginot Line, a defensive string of large and small forts built during the years between World War I and World War II, was intended to forestall another invasion by aggressive Germany. Despite the Treaty of Versailles, France saw that it was only a matter of time before Germany would rise again and threaten France. News of northern neighbor Belgium’s neutrality left France with an exposed flank, which would ultimately be the Maginot Line’s weak point-the Germans were able to outflank the line almost entirely, readily conceding the Line’s impregnability while conquering the country.