Choose an outcome first. Pressure for reform, the fall of allied governments and the breakup of the Soviet state were connected, but they need different explanations.
Which outcome are you explaining?
Why reform became urgent
- Weak productivity and shortages damaged confidence.
- Military and bloc commitments absorbed civilian resources.
- Renewed US arms competition added pressure.
These conditions help explain why continued confrontation and unchanged domestic policy looked increasingly costly.
Pressure alone does not explain why a leader chose openness or non-intervention rather than tighter repression.
Why Eastern Europe changed in 1989
- Local opposition and migration challenged regimes.
- Gorbachev stopped guaranteeing their survival through Soviet force.
- Polish negotiations and the opening of the Berlin Wall changed expectations.
Local pressure gained a different result when an external military guarantee was removed.
Eastern European changes do not by themselves explain every step in the later dissolution of the Soviet Union.
Why the USSR dissolved in 1991
- Economic failure and political openness weakened the centre.
- Republic leaders and independence movements asserted power.
- The failed August coup further discredited central authority.
Longer-term weakness combined with political struggles and a failed attempt to reverse change, making the union harder to preserve.
A final trigger should not replace explanation of the conditions that gave it such force.