Defence Studies: Gorbachev's Era saw perhaps the most sweeping changes in Soviet military doctrine. In the early part of this period, the doctrine changed very little from what it had been under Brezhnev. In the mid-1980s, Gorbachev's perestroika (restructuring) markedly accelerated changes in military doctrine. An emphasis on the strategic defense, rather than preemptive offensive conventional strikes, marked the doctrine emerging from this period