s the provisions of the SALT-2 agreement prohibited the deployment of more than one new missile (which became RT-23UTTh), it was officially declared by the Soviet Union that the SS-25 Topol was developed to upgrade the silo based SS-13 RT-2P. The US government disputed this view, contending that the missile was clearly more than 5% larger and had twice the throw-weight as the SS-13. An SS-25 with two MIRVs may have been tested in 1991, and the missile was tested at least once with four MIRV warheads, but no further development of a mutiple warhead version was carried out. This became an issue during the conclusion of the 1991 START negotiations, at which time the US pressed for a definition of "downloading" (removing warheads from missiles) that would complicate any Soviet attempt suddenly to deploy multiple warheads on the SS-25.

Russia plans to to reequip approximately 400 silos in which obsolete SS-11, SS-13 and SS-17 missiles are located. Under the START-II Treaty Russia is permitted to place 90 single- warhead solid fuel missiles in reequipped SS-18 ICBM silos. On-site inspection of SS-18 heavy ICBM silo conversions, to guard against a break-out scenario involving speedy reconversion of SS-18 silos, is one particularly important aspect of START II verification in accordance with the Protocol on Procedures Governing Elimination of Heavy ICBMs and on Procedures Governing Conversion of Silo Launchers of Heavy ICBMs. US inspectors could either physically witness the pouring of the five meters of concrete in the bottom of the silo or measure silo depth before and after the concrete was poured.