Russia is in the middle of modernizing its nuclear forces, replacing Soviet-era ballistic missiles with fewer improved missiles. In a decade, almost all Soviet-era weapons will be gone, leaving a smaller but still effective force that will be more mobile than what it replaced. As of early 2013, Russia has a stockpile of approximately 4,500 nuclear warheads, of which roughly 1,800 strategic warheads are deployed on missiles and at bomber bases. Another 700 strategic warheads are in storage, along with 2,000 nonstrategic warheads. There is some uncertainty in these estimates because Russia does not disclose how many nuclear weapons it has and the United States has stopped releasing data supplied by Russia under strategic arms reduction agreements. The authors use public statements made by Russian officials, newspaper articles, observations from commercial satellite images, private conversations with government officials, and analysis of Russian nuclear forces over many years to provide the best available unclassified estimate of Russian nuclear forces.