The history of the creation of this aircraft began in 1961, when the design bureau of Artem Mikoyan began work on a new-generation fighter, conventionally called it the MiG-23, and it was intended to replace the MiG-21, at that time the MiG-21 only began to enter the arsenal of the Air Force. Initially, a new aircraft was to be built using a number of elements of the design of its predecessor. The prototype of such an E-8/1 machine, piloted by test pilot GK Mosolov, first took off on April 17, 1962. The plane was made on a modern "longitudinal triplane" scheme. Its features were a small canard foreplane and a ventral variable geometry air intake. The fighter was supposed to be equipped with a Sapphire-21 radar (it was absent on the first test plane), and its weapons were to include R-13 guided missiles with a thermal guidance, which later were to be supplemented with medium-range missiles K-23 with a radar semi-active guidance system. In accordance with the fashion of that time, cannon armament was absent, since it was believed that the aircraft would be used mainly for supersonic interception of high-altitude high-speed targets, striking the enemy with missiles in the first attack; Maneuvering combat at subsonic speed was not given much importance, considering that a supersonic missile carrier operating in accordance with the "run and run" rule does not need to be drawn into close air combat.

During one of the test flights on September 11, 1962, an accident occurred. Mosolov catapulted and suffered serious injuries, and the plane was lost. By that time, the second experimental vehicle E-8/2 had already flown by almost two and a half months, but after the Mosolov accident, further work on the E-8 theme was decided to be discontinued. However, this did not mean a refusal to create a frontal fighter that was more perfect than the MiG-21. By the time the F-4C "Phantom-2" appeared in the US Air Force, it was the first serial tactical fighter in the world capable of firing a missile in combat at medium ranges. Other characteristics of this multipurpose aircraft also looked very impressive, which prompted the Soviet military and the Ministry of Aviation Industry (MAP) to hurry with an "adequate response".

Almost immediately after the termination of work on the E-8, the OKB Mikoyan began to create a completely new front-line fighter. Initially, the program was supposed to be implemented in two stages. At the first it was planned to create a plane with a triangular wing and a perspective engine R-27F-300. The maximum speed was to reach 2700 km / h (almost like the MiG-25), which implied the use of new construction materials and technologies. The machine was going to be equipped with a new Sapphire-23 radar and two or four all-range medium-range missiles K-23. It should be noted that earlier all front-line fighters of the Soviet Air Force were armed with guns and short-range missiles only, and medium-range missiles were equipped with only air defense interceptors designed to deal with non-lethal aircraft. Like the MiG-21, the new fighter had to be operated from ground airfields or concrete runways of the 2nd class.

​

​
This machine, designed to perform one task using two different aerodynamic concepts, The MiG-23PD was the first variant of the project. The aircraft 23-01, or MiG-23 PD (PD - lift engine - shortened take-off and landing variant), was designed in parallel to the 23-11 variable geometry wing variant, it had to be able to fly at speeds up to Mach 2.3 and at the same time being able to have short take-off and landing capability.
The outline of the design was developed in 1964, the construction began in 1965. The leading engineer of both experimental aircraft was VA Mikoyan - nephew of General Designer AI Mikoyan.
Engineers of the OKB Mikoyan chose a configuration for MiG-23PD, it was of a triangular wing with a horizontal  tail, as on the MiG-21. An all moving horizontal stabilizer or taileron.
The chosen scheme provided for the use of lifting turbojet engines during take-off and landing, the main turbofan engine was powered by air only through two side semi-circular air intakes  which are similar to the intakes fitted to the Mirage III. 
In the middle of the fuselage, two RD-36-35 lifting jet engines of the OKB PA Kolesov design were placed vertically, but with a small angle, with a pull of 2303 daN (2350 kgf) each. They were used only on takeoff and landing. At these short intervals with the help of a power cylinder, the rotary cover-hatch with shutters located in the upper part of the fuselage was opened, providing power to the two lifting engines for maximum air flow.
The exhaust nozzles located under the fuselage were equipped with rotary grilles. They acted as traction reversers during landing, and on takeoff, on the contrary, allowed to summarize the thrust of all three jet engines.
The main engine was the R-27-300 of maximum thrust at takeoff of (5200 kgf) and an afterburning thrust of (7800 kgf). It was specially designed for the MiG-23. 
Its Armament consisted of one two-barreled gun GSh-23 under the fuselage and two missiles K-23 under the wing.
On April 3, 1967 23-01 took to the air at the hands of PM Ostapenko . Then a series of complex tests was started, led by engineer VM Timofeev. They allowed simultaneously with Ostapenko's flights to accumulate piloting experience for the air parade in Domodedovo on July 9, 1967, dedicated to the 50th anniversary of the October Revolution.
Another pilot OKB AV Fedotov also performed several flights on 23-01. This experienced aircraft had a very short life. After Ostapenko's flight to Domodedovo, flight tests 23-01 were discontinued in favor of 23-11 with a variable sweep of the wing. Thus, all the flight regimes were practically not studied except for the takeoff and landing characteristics.
 

​

However, the constantly changing views on the combat use of aviation have led to further tightening of the requirements for the takeoff and landing characteristics of tactical aircraft. This was primarily contributed to the appearance around the early 1960s in both in the USA and in the USSR, of tactical nuclear munitions that could be suspended under fighter-bomber class aircraft, and also used tactical missiles. The strategists of both sides believed that, in a full-scale war, large airfields with concreted runways would become too vulnerable. Therefore, the aircraft would have to relocate to reserve sites of limited size or die at their airbases. Under the influence of such views, the OKB together with TsAGI prepared proposals for the second stage of the MiG-23 program, during which it was planned to create a more advanced aircraft capable of being operated from shortened runways. This could be achieved in two ways: through the use of lifting engines (PD) or the use of a wing with variable sweep. Both of these trends at that time entered into fashion in the USSR and abroad.

TsAGI, relying on a large amount of fundamental research, insistently recommended the use of a wing of variable geometry. Studies in which GV Aleksandrov, SM Belotserkovsky, GS Byshgens and other leading Russian aerodynamics scientists took part showed that using a short sweep (10-15 degrees) with a wing with a large elongation and powerful mechanization, it is possible to significantly improve  and reduce the minimum permissible flight speed and take off distance. With a sweep of 35-45 degrees, good maneuverability and high aerodynamic quality at transonic modes were provided. Setting the wing at an angle of 60-70 degrees, it was possible to achieve high supersonic speeds, in addition, this regime was very favorable for flight at low altitudes at high  speeds. The use of such a wing made it possible to create a multi-mode combat aircraft capable of solving the tasks of a front-line fighter, an interceptor and a low-altitude fighter-bomber.

​

The machine was conceived to be relatively inexpensive, able to be effectively used in small wars, to solve air defense missions and be widely supplied to "fraternal" countries. The main advantages of the aircraft were to be high speed and climb rate, long range and duration of flight. Since conducting maneuverable air combat was not considered a priority, the maximum operational overload was reduced to 5.0, which made it possible to make the glider easier. Thus, the MiG-23 during the design was considered as a limited maneuverable aircraft, like the interceptor MiG-25P. This featured the new machine from the MiG-21, designed for maximum operational overload of 7.0-8.5 (depending on the modification), and later created many problems.

The difficulties in ensuring the stability and controllability that have arisen in connection with the use of the new wing were successfully solved by the specialists of TsAGI due to the effect they detected: the aerodynamic center of the wing changed with the sweep angle very little if it had a root glove at the location of the axis of rotation of the wing pivot . Studies have proved the possibility of creating a universal layout of the aircraft, which formed the basis of the new MiG, as well as the Su-24 bomber. The MiG-23 aerodynamics was tested in the TsAGI wind tunnels T-106M and T-109 using large-scale models. The importance of these works is evidenced by the fact that in 1975 the fundamental research of TsAGI on aircraft with variable geometry of the wing was marked by the State Prize.

Probably, the appearance of the new MiG was formed and not without Western influence. At the command of the Air Force and the political leadership of the country made a great impression of the design characteristics and multi-functionality of the American fighter-bomber F-111, equipped with a wing with variable sweep. However, the plane, which was created in OKB Mikoyan, unlike the American machine, remained single seat aircraft and had a much smaller mass.

Improvement of the take off and landing characteristics of a prospective fighter by using lift engines had fewer adherents among the representatives of scientific aerodynamic studies, although it was supported by a number of authoritative specialists. As a result, it was decided in parallel the creation of a fighter with variable geometry of the wing to build a MiG with additional lift engines.

The technical design of the MiG-23 "second stage" in OKB Mikoyan began in 1964. The machine with a wing of variable geometry was designated "23-11". The design of the fighter "23-11" was carried out at a rapid pace. The work was further accelerated after the publication in 1965 of the order of the Ministry of defence, which determined their main directions. By this document, the creation of the mechanism for turning the wing was entrusted to the MKB "Rodina" (chief designer of Selivanov). In January-March 1966, the preliminary design of the aircraft was completed. The technical management of the program was entrusted to A Andreev.

​

The aircraft "23-11", like "23-01", was equipped with a cruise main engine R-27F-300. The high-mounted wing, equipped with flaps  and slats, could be deployed at the sweep angles of 16, 45 and 7 degrees.  The landing gear of the original design was retracted into the fuselage, occupying a minimum volume. The main landing gear, large-diameter wheels of  the KT- 133 model of 830x225 mm dimensions, which together with the front wheel in the size of 520x125 mm provided excellent stability on the ground runway. For directional stability at high speed, the airplane was fitted with an original ventral fin that was folded during landing (the first such design appeared on the experimental E-8, later it was borrowed by the Chinese when creating the J-8-II.) The design of the airframe is made with wide use of steel alloys. Of these, in particular, the main bearing element of the aircraft was welded-the central section of the fuselage used as an integral fuel tank. The cockpit with a low pilot seating position was enclosed by a relatively small canopy, which reduced drag. Such a glazing gave the pilot a good overview ahead, but limited the view sideways and back, which was partially compensated by the installation of the periscope. Armament, including K-23 and K-13 missiles, these  were deployed on two underwing hardpoints and two under-body suspension assemblies.

The crew of the first experienced "23-11 / 1" included: chief-pilot AV Fedotov, leading engineer V. A. Mikoyan and aircraft engineer V. I. Skotnikov. The first time the plane ascended to the sky on July 9, 1967 - this date can be considered the birthday of the MiG-23. Already during the second flight, Fedotov changed the sweep of the wing in the whole range of angles and, as the OKB test pilot BA Orlov recalled, remained quite pleased with the behavior of the aircraft. This estimate is confirmed by a record in the onboard notebook made by Fedotov: "The flight with a sweep from 16 to 72 degrees, for a first flight."it was Great! ".

Soon the first aircraft was joined by the "23-11 / 2" (leading engineer Yu.N. Fedulov) and "23-11 / 3" (leading engineer A. N. Soshin). On the last plane, for the first time, the Sapphire-23 radar was installed. The work on testing a complex and whimsical radar complex was conducted with great effort, in three shifts. Simultaneously, "Sapphire" was developed in the LII flying laboratory, created on the basis of an experienced passenger aircraft Tu-110. Later, the aircrafts "23-11 / 4", "23-11 / 5", "23-11 / 6" and "23-11 / 9" joined the tests. In total, the program of factory and state tests of the MiG-23 involved nine vehicles. In the flights participated "Mikoyan`s" pilots: PM Ostapenko, MM Komarov, BA Orlov and AG Fastovets, as well as testers of the flying station in Zhukovsky and Air Force personnel . As BA Orlov wrote, MiG-23 made a generally good impression on him. The plane was liked by its "flying characteristics" and a good overview from the cabin. However, the handling of the fighter left much to be desired. In addition to the already mentioned leading engineers, the tests were provided by: AM Gerasimenko, VD Troitsky, VS Romanychev. VN Utkin, AS Vyushkov and many other specialists. Almost the whole staff of aircraft engineers of the OKB and of flying station in Zhukovsky were involved.