flight-design tests of the R-36MUTTKh began on 31 October 1977 and in November 1979 the flight tests of the MIRVed missile were completed. The first three regiments were put on alert on 18 September 1979. During 1980 a total of 120 missiles were deployed, replacing the last remaining R-36 missiles. In 1982–1983 the remaining R-36M missiles were also replaced with the new R-36MUTTKh and the total number of deployed missiles reached the maximum 308 ceiling established in the SALT-1 treaty. The R-36MUTTKh force had the estimated capability to destroy 65 to 80 percent of US ICBM silos using two nuclear warheads against each. Even after this type of attack, it was estimated that more than 1000 R-36MUTTKh warheads would be available for further strikes against targets in the US. After 2009, the R-36MUTTKh were all eliminated in favor of the newer R-36M2. R-36M2 Voevoda (SS-18 Mod 5) This newer, more accurate version placed in converted silos allowed the R-36M family to remain the bulwark of the SRF’s hard-target-kill capability. The R-36M2 carries 10 MIRVs, each having a nearly twice the yield of the R-36MUTTKh warheads according to Western estimates (approximately 750 kt to 1 Mt), though Russian sources suggest a yield of 550–750 kt each. The increase in the R-36M2's warhead yield, along with improved accuracy, would, under the START treaty, help allow the Russians to maintain their hard-target-kill wartime requirements even with the 50 percent cut in heavy ICBMs the START agreement required. The technical proposals to build a modernized heavy ICBM were made in June 1979. The missile subsequently received the designation R-36M2 Voevoda and the industrial index number 15A18M. The design of the R-36M2 was completed in June 1982. The R-36M2 had a series of new engineering features. The engine of the second stage is completely built into the fuel tank (earlier this was only used on SLBMs) and the design of the transport-launching canister was altered. Unlike the R-36M, the 10 warheads on the post-boost vehicle are located on a special frame in two circles. The flight tests of the R-36M2 equipped with 10 MIRVs began in March 1986 and were completed in March 1988. The first regiment with these missiles was put on alert on 30 July 1988 and was deployed on 11 August 1988. This is the only variant still operational. One of the missile's most important features is its storage/basing in a container,