Short answers, pulled from the story.
START II was a bilateral arms reduction treaty between the United States and Russia, signed on the 3rd of January 1993 by US president George H. W. Bush and Russian president Boris Yeltsin. It banned multiple independently targetable reentry vehicles, or MIRVs, on intercontinental ballistic missiles, earning the informal name the De-MIRVing Agreement.
The State Duma postponed ratification repeatedly to protest American military actions in Iraq and Kosovo and to oppose the expansion of NATO into Eastern Europe. The Duma finally ratified on the 14th of April 2000, attaching conditions requiring the US to preserve the Anti-Ballistic Missile Treaty and ratify a September 1997 addendum on missile defense demarcation.
The United States withdrew from the Anti-Ballistic Missile Treaty on the 13th of June 2002, removing the central condition Russia had required for its own ratification. Russia announced the following day that it would no longer consider itself bound by START II. The US Senate had also never ratified the September 1997 addendum Russia had required.
The Strategic Offensive Reductions Treaty, or SORT, replaced START II. George W. Bush and Vladimir Putin signed it at the Moscow Summit on the 24th of May 2002, committing both countries to reduce operationally deployed strategic warheads to between 1,700 and 2,200 by 2012.
The United States completed its unilateral withdrawal from MIRVed land-based missiles by the 19th of September 2005, including the full deactivation of the LGM-118 Peacekeeper. As of 2011, the Minuteman III was the only remaining American land-based operational ICBM, capable of carrying a potential maximum of three warheads.
Russia retained 54 RS-20/R-36M (SS-18 Satan) missiles with 10 warheads each, 40 RS-18/UR-100N (SS-19 Stiletto) missiles with 6 warheads each, and 24 RS-24 Yars missiles with 3 warheads each. The total warhead count across these three types exceeded 850.