Let's look at what the US and, further, the USSR, have been doing.
By 1945 the United States had launched its first sounding rocket, the WAC Corporal. Then those were succeeded by a menagerie of other sounding rockets, the most successful of which was the Cadet rocket, operational by late 1947. For the most part, though, the US had little knowledge of the developments in Europe. It wasn’t till 1947 that they saw the Europeans launching their first ballistic missiles, and here was the United States of America, the land of freedom and ever so a world leader, left behind by those damned European extremists!
This period in 1947, which came to be named the “Gap Scare of ‘47”, led to the creation of the Air Force Missile Division, and a program to develop ballistic missiles, as well IRBMs which were also under consideration began. Wernher von Braun left Aerojet, in search of grander aspirations and joined the Air Force Missile Division. At around the same time, Frank Malina left Aerojet Corporation too, daunted by the growing pressures of the missile industry and its weapons-oriented nature.
Finally, it was decided in AFMD that an IRBM project should be started. This missile project came to be named the Lares IRBM, a quite fitting name indeed, for Lares were Roman deities that guarded hearths and boundaries, and their father was Mercury, the god of travellers and boundaries. In 1949, the first US ballistic missile was launched and by 1953, the first Lares IRBM had been launched. They’d made decent progress in catching up, with the Soviets having launched their first IRBM by 1951 and the West Europeans in 1952.
Now, on to intercontinental aspirations.
The Soviet Union had a need for ICBMs. They didn’t have a bomber fleet that could drop nukes over the Americans willy-nilly, and to them, it appeared that the Americans very well could bomb them with nukes too. They had invented the nuke first sure, they’d used the nukes in the Pacific War too, but their stockpile still couldn’t be used to bomb the Americans. Not even the Germans made good enough bombers for that.
So naturally, RENIT was selected to develop the Soviets’ first ICBM. Sergei Korolev would be the head designer for this project. This was a matter of utmost importance, thanks to a bunch of political maneuvering by Korolev to get to the top. Korolev began with the development of the R-15, and it would be fueled by kerosene and liquid oxygen. Despite the fact that liquid oxygen wasn’t particularly storable, even the most diehard storables fan in RENIT accepted that it would offer superior performance, which was important. Tanks and rocket engines hadn’t advanced enough that they could accept the loss in performance.
The Soviet brass had asked for a <300 ton ICBM with a range of at least 7,000 km. By 1952 it was clear that they couldn’t stay under 300 tons, and the final design ended up being a modest overweight, around 320 tons. In 1955 the world’s first ICBM, the R-15 was launched from Baikonur Cosmodrome. It was also capable of orbit – a 1.8 ton payload could be launched to low earth orbit. While the Soviets knew that they could launch a satellite by 1956 at least, a new ICBM project was already started during the testing period of the R-15, thanks to a new propellant discovered by the Americans in 1955.
Unsymmetrical dimethylhydrazine, or UDMH for short.
It offered enough performance, and thanks to the ever-improving performance of rocket engine and tank design, the R-16 as it was called by RENIT could launch the same payload as the R-15 while only weighing as much as half - 141 tons! Unlike Korolev's R-15, this R-16 was instead developed by the storables faction of RENIT.
With the R-16, also came Korolev’s demise. He’d been brash, arrogant, and stubborn. The others at RENIT tolerated him only because of the power that he gained, but with how poorly performing the R-15 seemed compared to the R-16, the others at RENIT took the opportunity to speak out against Korolev. It seemed enough to convince the guys at the top, and later in 1957 Korolev resigned rather than be demoted to being just a designer. Mikhail Tikhonravov, being the most uncontroversial choice for a successor, became head of RENIT.
R-15. Credit: Kirk, using Kerbal Space Program
R-16. From me, using Blender