Wikipedia
The Molniya-M (, meaning "lightning"), designation 8K78M, was a Russian (previously Soviet) carrier rocket derived from the R-7 Semyorka ICBM.
The original 8K78 booster had been the product of a rushed development program and its launch record was no better than the 8K72 Luna booster of 1958-60. As 1962 ended, there had been 12 launches of 8K78s, 10 of which failed (five Blok L failures, four Blok I failures, and one failure caused by the Blok A core stage). The two successful launches had had their probes ( Venera 1 and Mars 1) fail en route to their respective planetary targets. As such, work began at the Korolev Bureau to improve the basic 8K78 vehicle. The core and strap-ons engines were enhanced still further and the Kosberg Bureau completely redesigned the Blok I stage. The Blok L engine was also slightly enhanced.
The 8K78M was first launched in 1964 and had replaced its predecessor, Molniya, by the end of 1965. During 1967, the improved core stage and strap-ons from the Soyuz 11A57 were adopted and made standard on all R-7 based vehicles. It made 297 launches and experienced 21 failures, the last of which occurred on 21 June 2005 when a third stage malfunction prevented its payload, a Molniya-3K communications satellite from reaching orbit. There were no failures of Molniya-Ms that occurred in the first two minutes of the launch. The final flight of a Molniya-M lofted an Oko early warning satellite from Plesetsk on 30 September 2010 despite some apprehension that the launch vehicle, manufactured in 2005, had exceeded its storage life. It will be replaced by the Soyuz-2/ Fregat.
Although originally developed for planetary probes, those had switched to the larger Proton booster by the 1970s due to increasing mass and complexity. For most of its operational life, the Molniya-M was used to launch its namesake Molniya and also Oko satellites into Molniya orbits, orbits of high eccentricity that allow satellites to dwell over polar regions.