The German military historian Hans Delbrück said of this battle "there was no more important battle in the history of the world." ("The Barbarian Invasions", p. 441.) Had Charles Martel failed, Henry Hallam argued, there would have been no Charlemagne, no Holy Roman Empire or Papal States; all these depended upon Charles's containment of Islam from expanding into Europe while the Caliphate was unified and able to mount such a conquest. Another great mid era historian, Thomas Arnold, ranked the victory of Charles Martel even higher than the victory of Arminius in its impact on all of modern history: "Charles Martel's victory at Tours was among those signal deliverances which have affected for centuries the happiness of mankind." Louis Gustave and Charles Strauss said "The victory gained was decisive and final, The torrent of Arab conquest was rolled back and Europe was rescued from the threatened yoke of the Saracens."