 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".