On Aug. 20, 1968, about 200,000 Warsaw Pact troops and 5,000 tanks invaded Czechoslovakia to crush the "Prague Spring" -- a brief period of efforts to democratize socialism in the country.

On Aug. 20, 1977, the first U.S. Voyager spacecraft (one of two launched in 1977) left Cape Canaveral, Fla., bound for Jupiter and Saturn.

UPI Almanac for Wednesday, Aug. 20, 2014

UPI Almanac for Tuesday, Aug. 20, 2013.

UPI Almanac for Monday, Aug. 20, 2012.

UPI Almanac for Wednesday, Aug. 20, 2008.

UPI Almanac for Monday, Aug. 20, 2007.

Today is Sunday, Aug. 20, the 232nd day of 2006 with 133 to follow.

Today is Saturday, Aug. 20, the 232nd day of 2005 with 133 to follow.

The weekly UPI Almanac package for August 15-21, 2005.

Today is Friday, Aug. 20, the 233rd day of 2004 with 133 to follow.

Today is Wednesday, Aug. 20, the 232nd day of 2003 with 133 to follow.

The United States struck back on this date in 1998, when American missiles targeted sites in Afghanistan and Sudan said to be linked with terrorists. The attacks came in response to the bombings of the U.S. embassies in Kenya and Tanzania 13 days earlier.

Today is Tuesday, Aug. 20, the 232nd day of 2002 with 133 to follow.

The weekly package of A Blast from the Past for Aug. 19-25.