The Holy Roman-French War (26 February 1312-29 January 1315) was a war fought between the Kingdom of France and the Holy Roman Empire during the early 14th century. The war began when Emperor Henry VII of Germany declared war on King Philip IV of France with the goal of acquiring the Duchy of Bar in eastern France, and Imperial armies invaded France through the Low Countries and through Burgundy. The French royal army, commanded by King Philip himself, marched to Langres to do battle with the invading German armies, and it was smashed by Duke Frederick IV of Austria's larger army of mercenaries on 11 November 1312. The amazing Austrian victory over France did not end the war, however. The death of Emperor Henry VII of Germany destabilized the empire, and the death of his predecessor Henry VIII of Germany after a three-day reign led to the Dutchman William III of Holland becoming the new Emperor. Frederick of Austria decided to seize power and return his family, the Habsburg dynasty, to power. The French and Imperial forces clashed along the frontier for years, and the rebels under Frederick at times marched through French territory, using France as a springboard for incursions into western Germany. The war came to an end with William's defeat by the rebels in January 1315, as the Germans lost their casus belli with the change of ruler.