Editing Martin P4M Mercator (section)

==Operational history==
[[File:Martin P4M-1 Mercator of VP-21 in flight in the early 1950s (NH 101801-KN).jpg|thumb|right|P4M-1 of [[VP-21 (1943-69)|VP-21]]]]
The US Navy chose the smaller, simpler, cheaper and better performing P2V Neptune for the maritime patrol requirement, but nineteen aircraft were ordered in 1947 for high-speed minelaying purposes. The P4M entered service with [[VP-21 (1943-69)|Patrol Squadron 21 (VP-21)]] in 1950, the squadron deploying to [[NAS Port Lyautey]] in [[French protectorate of Morocco|French Morocco]].<ref name="Ferret p217">Dorr and Burgess 1993, p.217.</ref> It remained in use with VP-21 until February 1953.<ref name="DANAS v2 p125">Roberts 2000, p.125.</ref>

From 1951, the 18 surviving production P4Ms were modified for the electronic reconnaissance (or [[SIGINT]], for ''signals intelligence'') mission as the '''P4M-1Q''', to replace the [[PB4Y-2 Privateer]]. The crew was increased to 14 and later 16 to operate all the surveillance gear, and the aircraft was fitted with a large number of different antennae.<ref name="WoF p141-2">Lake and Dorr 2000, pp. 141–142.</ref>

[[File:Martin P4M Mercator VQ-2 06.09.56.jpg|thumb|right|P4M-1Q Mercator of VQ-2 electronics reconnaissance squadron in September 1956 - note extra radar 'bulges' on this variant]]

Starting in October 1951, electronic surveillance missions were flown from [[U.S. Naval Station Sangley Point]] in the [[Philippines]], later from [[Naval Air Station Iwakuni]], [[Japan]], and [[Naval Air Station Atsugi]], Japan, by a secretive unit that eventually gained the designation [[VQ-1|Fleet Air Reconnaissance Squadron One (VQ-1)]]. Long missions were flown along the coast (about {{cvt|30|nmi|km|disp=or}} offshore) of Vietnam, China, North Korea and the eastern Soviet Union, and were of a highly secret nature; the aircraft sometimes masqueraded as regular P2V Neptunes in radio communications, and often flew with false [[United States military aircraft serials#United States Navy and Marine Corps|serial numbers]] (Bureau Numbers) painted under the tail. Operational missions were always flown at night, during the dark with the moon when possible, and with no external running lights.<ref name="Ferret p217,220">Dorr and Burgess 1993, pp. 217, 220.</ref>

The Mercators were replaced by the [[A-3 Skywarrior|EA-3B Skywarrior]], which, being carrier-based, had a greater degree of flexibility, and the larger [[EC-121 Warning Star|Lockheed WV-2Q Warning Star]]. Final withdrawal from service was in 1960 after which all of the remaining P4Ms were scrapped.<ref name="Ferret p222">Dorr and Burgess 1993, p.222.</ref>