 The MTT's mission during a crisis would be to fight alongside, and provide replacements for, the personnel of the regular armed force; to help protect such strategic infrastructure as bridges, highways, and railroads; and to carry out any other measures that might be needed to immobilize, wear down, or ultimately destroy the enemy.By the beginning of the 1980s, MTT members were extensively involved in the construction of tunnels throughout the island, which would be used as shelter for the population in the event of an attack.As a result of Cuba's continuing economic difficulties during the 1990s, the time that MTT members have spent in training and preparing for their various defense-related activities has been reduced.