The Soviet Union did, in fact, have ICBMs with 20 MT warheads. As many as 210 R-36 in 1973, down to 30 R-36M/R-36MUTTH in 1978-1990 (they probably stayed longer while R-36MUTTH were being withdrawn from service). See Table 1 in russianforces.org/podvi…
The Soviet Union did, in fact, have ICBMs with 20 MT warheads. As many as 210 R-36 in 1973, down to 30 R-36M/R-36MUTTH in 1978-1990 (they probably stayed longer while R-36MUTTH were being withdrawn from service). See Table 1 in https://russianforces.org/podvig/2008/06/the_window_of_vulnerability_that_wasnt.html