Since the early 1980s, China pursued what some observers described as a semi-secret campaign against Vietnam that was more than a series of border incidents and less than a limited small-scale war. The Vietnamese called it a "multifaceted war of sabotage." Hanoi officials have described the assaults as comprising steady harassment by artillery fire, intrusions on land by infantry patrols, naval intrusions, and mine planting both at sea and in the riverways. Chinese clandestine activity (the "sabotage" aspect) for the most part was directed against the ethnic minorities of the border region. According to the Hanoi press, teams of Chinese agents systematically sabotaged mountain agricultural production centers as well as lowland port, transportation, and communication facilities. Psychological warfare operations were an integral part of the campaign, as was what the Vietnamese called "economic warfare"—encouragement of Vietnamese villagers along the border to engage in smuggling, currency speculation, and hoarding of goods in short supply.