Prompt Global Strike

Prompt Global Strike (PGS) is a United States military effort to develop a system that can deliver a precision conventional weapon strike anywhere in the world within one hour, in a similar manner to a nuclear ICBM. In April 2010, Marine Corps General James Cartwright explained the system's rationale, stating that "Today, unless you want to go nuclear, [the conventional military response time is] measured in days, maybe weeks". A PGS system could also be useful during a nuclear conflict, potentially replacing nuclear weapons against 30 percent of targets. The PGS program encompasses numerous technologies, including conventional surface-launched rockets and air-launched hypersonic missiles, although no specific PGS system has yet been finalized.

System
The PGS system will be designed to complement existing American rapid-response forces, such as Forward Deployed Forces, Air Expeditionary Groups (which can deploy within 48 hours) and carrier battle groups (which can respond within 96 hours). Possible delivery systems include:
 * a rocket similar to existing ICBMs, launched from land or via submarine
 * an air-launched hypersonic cruise missile, such as the Boeing X-51 or Advanced Hypersonic Weapon
 * a kinetic weapon launched from an orbiting space platform

In 2010, the United States Air Force prototyped a PGS system based on a modified Minuteman III ICBM. In March 2011, Air Force Major General David Scott stated that the service had no plans to use a sea- or land-based ICBM system for Prompt Global Strike, as they would be expensive to develop and potentially "dangerous." Instead, efforts would focus on a hypersonic glider. However, the following day, Air Force Chief of Staff Norton Schwartz said that an ICBM-based PGS system was still an option.

Background
The administration of George W. Bush considered developing such a weapon in the 2000s, but rejected the idea because of fears that an ICBM-launched weapon would trigger the Russian nuclear-launch warning system, potentially provoking a nuclear war. However, the Obama administration continued development of the system later in the decade.

A potential enemy cannot be certain that a launched ICBM contains only a conventional warhead, not a nuclear one. It is thus currently unclear what design features or precautions could convince China and Russia, two countries with launch-detection systems and nuclear ICBMs, to ignore their early-warning systems. Current ideas include a low-trajectory missile design, or allowing Russian and Chinese inspection of PGS missile sites.

On 11 April 2010, United States Secretary of Defense Robert Gates indicated that the United States already had a Prompt Global Strike capability. This coincided with the New START disarmament treaty signed on 8 April 2010, which set new, lower limits on ballistic missiles and their warheads. The treaty does not distinguish between conventional and nuclear versions of weapons, meaning any ballistic PGS missiles and warheads would count toward the new limit. However, the U.S. State Department has stated that this does not constrain plans for PGS deployment, since current plans do not come near the limits.

2011 AHW test
On 18 November 2011, the first Advanced Hypersonic Weapon (AHW) glide vehicle was successfully tested by the U.S. Army Space and Missile Defense Command as part of the Prompt Global Strike program. The missile was launched from the Pacific Missile Range Facility in Hawaii, and struck a target at the Reagan Test Site on Kwajalein Atoll, over 3700 km away, in under 30 minutes. The prototype, which incorporated technologies developed by Sandia National Laboratories, was used to gather data to assist the development of future hypersonic warheads.

Submarine option
In January 2012, the Pentagon stated that the platform would be submarine-based. However, practical efforts to develop the PGS system were delayed by fears of accidentally starting a nuclear conflict.

Russian response
In December 2010, Russian military experts indicated that the forthcoming S-500 missile defense system would include anti-hypersonic defenses. In December 2012, commenting on the development of a replacement for its R-36M2 Voevoda ICBM, the commander of the Russian Strategic Missile Forces, Sergey Karakaev, stated that the missile will allow Russia "to realize such opportunities as the creation of high precision strategic weapons with non-nuclear warheads and a practically global range. Russia can create non-nuclear, high precision weapons based on intercontinental rockets in the event that the USA also works on designing such a weapon".