From October 1964 the North Koreans increased the infiltration of intelligence-gatherers and propagandists into the South. By October 1966, more than 30 South Korean soldiers and at least 10 civilians had been killed in clashes with North Korean infiltrators; however, no similar clashes had taken place along the U.S.-controlled section of the DMZ. In October 1966, South Korea staged a retaliatory attack without seeking the approval of General Bonesteel, causing tension between the U.S. command, which wished to avoid violations of the armistice, and the South Koreans, who were suffering ongoing losses. Following the first KPA attack on US forces in November 1966, General Bonesteel formed a working group to analyse the North Korean strategy and develop a counter-strategy to defeat it. Finding the existing U.S. Army tactical doctrines to be inapplicable to the situation they were facing, the working group developed its own doctrine to meet its operational needs. Three types of operations were identified: first to guard against infiltration across the DMZ; second was a similar naval effort along the coasts; and third was counterguerrilla operations in the interior. All three types of operations had to be accomplished without jeopardizing the conventional defense of South Korea or escalating the conflict from low-intensity to a full war.. How many minimum South Korean soldiers and civilians were killed by October 1966?