risky subversive activity. It was only after the failure of Franco's onslaught in the winter of 1936–37, when it became clear the war would last longer and the front lines had stabilised, that a fifth column did emerge, though it was never as powerful or extensive as the Republicans feared; it largely focused on mutual assistance, espionage and undermining Republican morale, eschewing terrorist activities such as bombings and assassinations. While fifth columnists did contribute to the Nationalist war effort, the fall of Madrid was not caused by internal subversion but defeat in battle. The largest and most efficient of these groups was about 6000 strong and was a Falangist women's welfare network known as Hermanidad Auxilio Azul María Paz. As early as 11 May 1931, when mob violence against the Republic's perceived enemies had led to the burning of churches, convents, and religious schools, the Church had sometimes been seen as the ally of the authoritarian right. The academic Mary Vincent has written: "There was no doubt that the Church would line up with the rebels against the Republic. The Jesuit priests of the city of Salamanca were among the first volunteers to present themselves to the military authorities.... The tragedy of the Second Republic was that it abetted its own destruction; the tragedy of the Church was that it became so closely allied with its self-styled defenders". During the war, the Nationalists claimed that 20,000 priests had been killed; the figure is now put at 4,184 priests, 2,365 members of other religious institutes and 283 nuns, the vast majority during the summer of 1936. Payne has called the terror the "most extensive and violent persecution of Catholicism in Western History, in some way even more intense than that of the French Revolution", leaving Catholics with little alternative, and driving them to the Nationalists even more than it would have been expected. Death toll Figures for the Red Terror range from 38,000 to 72,344. Historian Beevor "reckons Franco's ensuing 'white terror' claimed 200,000 lives. The 'red terror' had already killed 38,000." According to Julio de la Cueva, the toll of the Red Terror was 72,344 lives. Hugh Thomas and Paul Preston said that the death toll was 55,000, and Spanish historian Julian Casanova said that the death toll was fewer than 60,000. Previously, Payne had suggested, "The toll taken by the respective terrors may never be known exactly. The left