In September 1833 Darwin set out to cross the Argentine pampas, heading for Buenos Aires. Immediately he found himself in the midst of a bitter struggle between the local Indians and the forces of General Rosas, who were engaged in a policy of extermination. ' I was made vividly aware of the relentless struggle for existence going on around me. Who would have believed, in a Christian country, that such atrocities could be committed? '