The A-6 was designed in response to a 1957 requirement issued by the Bureau of Aeronautics for an all-weather attack aircraft for Navy long-range interdiction missions and with short takeoff and landing (STOL) capability for Marine close air support.

During the Gulf War, a combination of U.S. Navy and U.S. Marine Corps A-6s conducted in excess of 4,700 combat sorties against a variety of Iraqi ground-based targets.

During the 1990s, the A-6 was intended to be superseded by the McDonnell Douglas A-12 Avenger II, but this program was ultimately canceled due to cost overruns.

Thus, when the A-6E was scheduled for retirement, its precision strike mission was initially taken over by the Grumman F-14 Tomcat equipped with a LANTIRN pod, and later passed on to the Boeing F/A-18E/F Super Hornet.

As a result of the fair-weather limitation of the propeller-driven A-1 Skyraider in the Korean War and the advent of turbine engines, the United States Navy issued preliminary requirements in 1955 for an all-weather carrier-based attack aircraft.

Aviation authors Bill Gunston and Peter Gilchrist observe that this specification was shaped by the service's Korean War experiences, during which air support had been frequently unavailable unless fair weather conditions were present.

[4] In response to the RFP, a total of eleven design proposals were submitted by eight different companies, including Bell, Boeing, Douglas, Grumman, Lockheed, Martin, North American, and Vought.

This design experience was taken into consideration by NASA in their November 1962 decision to choose Grumman over other companies like General Dynamics-Convair (the F-111 had computerized avionics capabilities comparable to the A-6, but did not fly until 1964) to build the Lunar Excursion Module, which was a small-sized spacecraft with two onboard computers.

The very advanced navigation and attack equipment required a lot of development and changes had to be made to correct aerodynamic deficiencies and remove unwanted features.

[13] During February 1963, the A-6 was introduced to service with the US Navy; at this point, the type was, according to Gunston and Gilchrist, "the first genuinely all-weather attack bomber in history".

The last variant to be produced was the A-6E, first introduced in 1972; it features extensive avionics improvements, including the new APQ-148 multimode radar, along with minor airframe refinements.

Intended to feature the General Electric F404 turbofan engine, as well as various avionics and airframe improvements, this variant was cancelled under the presumption that the in-development McDonnell Douglas A-12 Avenger II would be entering production before long.

[20] Other improvements were introduced to the fleet around this time, including GPS receivers, new computers and radar sets, more efficient J-52-409 engines, as well as increased compatibility with various additional missiles.

[21] The Grumman A-6 Intruder is a two-seat twin-engined monoplane, equipped to perform carrier-based attack missions regardless of prevailing weather or light conditions.

Together, the BACE systems greatly reduced the Maintenance Man-Hours per Flight Hour, a key index of the cost and effort needed to keep military aircraft operating.

The A-6 became both the U.S. Navy's and U.S. Marine Corps's principal medium and all-weather/night attack aircraft from the mid-1960s through the 1990s and as an aerial tanker either in the dedicated KA-6D version or by use of a buddy store (D-704).

The aircraft's long range and heavy payload (18,000 pounds or 8,200 kilograms) coupled with its ability to fly in all weather made it invaluable during the war.

However, its typical mission profile of flying low to deliver its payload made it especially vulnerable to anti-aircraft fire, and in the eight years the Intruder was used during the Vietnam War, the U.S. Navy and U.S. Marine Corps lost a total of 84 A-6 aircraft of various series.

[23] Although capable of embarking aboard aircraft carriers, most U.S. Marine Corps A-6 Intruders were shore based in South Vietnam at Chu Lai and Da Nang and in Nam Phong, Thailand.

[26] The Intruder's large blunt nose and slender tail inspired a number of nicknames, including "Double Ugly", "The Mighty Alpha Six", "Iron Tadpole" and also "Drumstick".

[27] Following the Gulf War, Intruders were used to patrol the no-fly zone in Iraq and provided air support for U.S. Marines during Operation Restore Hope in Somalia.

[29][30] Despite the production of new airframes in the 164XXX Bureau Number (BuNo) series just before and after the Gulf War, augmented by a rewinging program of older airframes, the A-6E and KA-6D were quickly phased out of service in the mid-1990s in a U.S. Navy cost-cutting move driven by the Office of the Secretary of Defense to reduce the number of different type/model/series (T/M/S) of aircraft in carrier air wings and U.S. Marine aircraft groups.

However, the availability of USAF Boeing KC-135 Stratotanker and McDonnell Douglas KC-10 Extender tankers modified to accommodate USN, USMC and NATO tactical aircraft in all recent conflicts was considered by certain senior decision makers in the Department of Defense to put a lesser premium on organic aerial refueling capability in the U.S. Navy's carrier air wings and self-contained range among carrier-based strike aircraft.

The initial version of the Intruder was built around the complex and advanced DIANE (Digital Integrated Attack/Navigation Equipment) suite, intended to provide a high degree of bombing accuracy even at night and in poor weather.

They were fitted with a "Trails/Roads Interdiction Multi-sensor" (TRIM) pod in the fuselage for FLIR and low-light TV cameras, as well as a "Black Crow" engine ignition detection system.

Beginning in 1979, all A-6Es were fitted with the AN/AAS-33 DRS (Detecting and Ranging Set), part of the 'Target Recognition and Attack Multi-Sensor' (TRAM) system, a small, gyroscopically stabilized turret, mounted under the nose of the aircraft, containing a forward-looking infra-red (FLIR) boresighted with a laser spot-tracker/designator and IBM AN/ASQ-155 computer.

In the early 1990s, some surviving A-6Es were upgraded under SWIP (Systems/Weapons Improvement Program) to enable them to use the latest precision-guided munitions, including AGM-65 Mavericks, AGM-84E SLAMs, AGM-62 Walleyes and the AGM-88 HARM anti-radiation missile as well as additional capability with the AGM-84 Harpoon.

The A-6F would have had totally new avionics, including a Norden AN/APQ-173 synthetic aperture radar and multi-function cockpit displays – the APQ-173 would have given the Intruder air-to-air capacity with provision for the AIM-120 AMRAAM.

An electronic warfare (EW)/Electronic countermeasures (ECW) version of the Intruder was developed early in the aircraft's life for the USMC, which needed a new ECM platform to replace its elderly F3D-2Q Skyknights.

An EW version of the Intruder, initially designated A2F-1H (rather than A2F-1Q, as "Q" was being split to relegate it to passive electronic warfare and "H" to active) and subsequently redesignated EA-6A, first flew on 26 April 1963.