The arrival in the region of rebel general Augusto Sandino's guerrilla forces in the 1920s caused even the most remote Mayangna communities to become embroiled in the conflict, and Mayangna men appear to have been in high demand from both Sandino’s men and the Marines as guides and boatmen, and even as fighters: a description of the Sandinista raiders who blew up the La Luz mine in 1928 notes that “among their number were several Sumu Indians armed with shotguns and machetes.” But the biggest threat to the Mayangna in the first half of the twentieth century was the loss of lands to mestizo settlers from Western Nicaragua, and destruction and theft of Mayangna natural resources. The rising price of copper meant the opening of a new mine at Rosita in 1959, which by 1970 had generated 40-50 million dollars for its American owners. But the discharge of toxic waste products into the local rivers devastated the ecosystems that the Mayangna communities traditionally depended on for their food supply. In Wasakin, only a few miles downriver from Rosita, these also caused “stomach pains, vomiting, vomiting blood, fevers, headaches and coughing” in those who bathed in or drank the water, eventually resulting in the deaths of up to three children a day in January and February 1979.