January 23. North Korea seizes U.S. Navy ship "Pueblo"; holds 83 on board as spies.     August 20. Czechoslovakia is invaded by USSR and Warsaw Pact forces to crush liberal counterrevolution. 

Before October 3, 1968, 25 launches of RT-2 ICBM were completed in Plesetsk; during the test on August 28, 1968, three RT-2 missiles blasted off simultaneously from their silos, 20 seconds after coded signal from Moscow. After October 1968, random testing of serial RT-2 missiles had been taking place.  Also during 1968, mobile ICBM RT-20 (SS-X-15) has been tested in Plesetsk. 12  launches were conducted. Reportedly,  eight launches resulted in failures, after which the project was terminated.