The day martial law was declared in Poland.
At 11pm, December 12, 1981, all telephone and telex communications were terminated. About 30 minutes later TV and radio went offline. The next day the Wojskowa Rada Ocalenia Narodowego (Military Taskforce for National Recovery) was established; martial law was declared by Wojciech Jaruzelski and the 586 days of what was to be the systematic limiting of human rights began.
Thousands of Solidarity party members, striking workers and activist students were imprisoned; hundreds murdered by what was the primary enforcement arm of the government - the ZOMO. Demonstrations and protests were brutally dispersed, all too frequently with live rounds. Abuses of government power ranged from covert assasinations of prominent Solidarity members to arresting students in schools for talking between classes. Strict rationing (already in place, but exacerbated as strikes and conflict continued) was enforced on almost all food products.
Martial law was declared unconstitutionally; Sejm was in session, and the Constitution states that decrees can be issued only between sessions, to be affirmed by the Sejm during the next session.
The official reason given was that the country's economic failure was imminent and the government was in danger of a coup instigated by the Solidarity party. Much later in the 1990s general Jaruzelski stated that there were pressures from the USSR and that Warsaw Pact forces would enter Poland as peacekeeping forces if martial law was not declared. The preparations for martial law have been in place since August 1980.
Sources:
http://polskaludowa.com/index.htm
http://www.gazeta.pl
I was six. I don't remember anything from that time, but I figure my instinctive apprehension at the sight of anyone in uniform (esp. green) and automatic dislike of authority of any sort has to come from somewhere...