This timeline diverged with the existence of Jan Zeldenthuis. He became a geologist; largely as a hobby he searched for new radioactive elements in the wild, attempting a safer follow-up to Marie Curie's work, and discovered natural thermopiles instead. In 1937, when Nikola Tesla was promoting Teleforce, the power requirements were scaring off potential customers — but Zeldenthuis was intrigued, and imagined vast artificial thermopiles with Teleforce sites atop them. He contacted Tesla and proposed the idea, and they worked together to develop a primitive RTG technology — still much more efficient than natural thermopiles. With an attached power source it attracted JP Morgan, who funded the development of and largely ran the sale of Teleforce towers.
They were ready when Germany invaded Poland, bringing WWII to Europe. The UK bought a handful of towers, covering its entire area; the USA bought several times as many, mainly for military bases, but a few port cities wanted them as well. France attempted to augment the Maginot Line with Teleforce towers, but not in time; two of them fell into the hands of the Nazi Germany, invading through the Ardennes, while a third was set up by French forces near Tours, stalling the invasion.
Hitler had believed the towers had some undiscovered weakness, which would provide the key to invading Britain; thus one of the captured towers was shipped to Germany for analysis. In the meantime, Hitler spoke proudly in diplomatic matters of the inevitable fall of the Tours tower, and that it would be followed by the fall of Britain. On the ground, Nazi forces had gotten as close to Tours as they could, using what terrain cover they could find, and no few units had been suddenly lost to streaks of lightning from the horizon. The report recommended high-speed rockets, but it was decoded by the Allies; one part, "its greatest weakness lies in the strength of its brothers", was trumpeted by Britain as a declaration of their unassailability under the towers. Peenemünde began work on rocket designs capable of over-the-horizon strikes against Teleforce towers, and Porsche switched gears to turn work on a nascent "electric transmission" into an RTG-powered tank, but neither was the weakness Hitler had faith in. The USSR continued their westward expansion into Eastern Europe, sticking to their pacts with Nazi Germany; while Morgan and Tesla were busily developing a second generation, many countries bought first-gen Teleforce towers, and a few were subverted by communist agents ahead of the Soviet advance. Nazi forces were left largely hemmed in by the towers. They struck out toward Scandinavia and the Near East… but they could only buy time until they could bring down the towers. An alliance with Japan and Italy bought them some face, officially forming the Axis.
Japan kept collecting parts of East Asia and Italy attacked around the Mediterranean in the summer of 1940, as in our timeline, but the big break came in 1941 with the deployment of the Kobra rocket and the Mungo spotter plane; the Kobra had considerable speed and accuracy, while the Mungo featured an RAS "reaction dodging system" that could toss it at 11 gees in short bursts. Together, they brought down the Tours tower, allowing Nazi Germany to complete its conquest of France and spread out over the Continent. With french ports, their navy made a savage dent in Allied shipping. Nazi reverse-engineering had worked well on the RTG, but lagged on the Teleforce weapons themselves; the USSR, on the other hand, had been working on lighter analogues of the Teleforce towers. The nazis fielded RTG-powered Maus tanks in the autumn, when the USA and UK navies were refitting their battleships with Eelcat Teleforce turrets. Unlike in our timeline, this both kept american battleships cycling, and provided a devastating defense against a potential Pearl Harbor attack; Imperial Japan held off on opening up the Pacific Theater.) Morgan and Tesla were also promising an answer to the Kobra and Mungo.
The geography of Britain allowed them to hold out until that answer arrived; in the winter, when the USSR began fielding an antipersonnel Teleforce weapon that could fit in the back of a partisan vehicle, the Allies began upgrading their towers with Gargoyle "rapid targeting" Teleforce weapons. While each tower's main gun was a ponderous thing, a handful of Gargoyles mounted on it could shoot down incoming Kobras. Soviet forces began using their light weapons in the same way. However, the Mungo moved perpendicularly, too dodgy for a reliable kill with either, leaving Nazi forces with an information advantage.
In early 1942, the USA fielded its own answers to the Mungo, the Foxbat and Thunderbird; the Foxbat was less a spotter than a spyplane, with jinking capability better than the Mungo, while the Thunderbird was an air superiority fighter with better jinking yet, and a light Teleforce weapon. The tide turned against Nazi Germany, but not for technological reasons; they were fielding Ratte tanks, powered by alphavoltaic NPUs and armed with Nazi Teleforce weapons, but the Nazi ideology was self-destructing. Hitler began implementing the Final Solution to prop it up, but he was assassinated in the summer; Goebbels was able to blame the jews for this, and succeed Hitler as Chancellor, but was unable to keep the german people with the cause as the Allies began to advance. As each city found itself at the front lines in turn, most decided they'd rather change sides than be the site of systematic bombing.
Stalin's ideology was undergoing more of a slow burn, as he purged more and more of the USSR's population, as if trying to compete with the kill count of Operation Barbarossa in our timeline. Imperial Japan saw this as a weakness, and began the Kamchatka Offensive in violation of the Soviet-Japanese Neutrality Pact a year earlier. Stalin, seeing this as a failure of the strategy the USSR countered the japanese attack on Mongolia with, struck against the islands of Japan. With Imperial Japan being ground under the Red Army, the japanese forces were cut off from their supply lines, and the USSR had only to wait for winter.
Tesla died of old age early in 1943, but his success had inspired a generation of innovators. While the Allies closed in on Nazi Germany with their own NPUs, the USSR's internal troubles came to a head in the 1943 Revolution. Rebel forces(called the Blue Army by Stalinist propaganda) had developed an "RTG meltdown" weapon, brought by suicide "bomber" close enough to deliver a deadly dose of radiation to Stalin himself. Several others were used at key locations, and several more fizzled, burning through the wearer and the floor without irradiating much. Video of Stalin's assassin was used to turn the people against the rebels, and the Blue Army fragmented, but with a death sentence over Stalin the USSR fragmented as well. Persistent infighting would last for years. Stalin died in november, as the final siege of Berlin began; Goebbels committed suicide in february of 1944. The Sixth Army of Imperial Japan bogged down in their conquest of China, settling on a border between China and Manchukuo in 1945.
WWII was officially over. Most of the developed nations were bombed out; the UK had suffered less than in our timeline, but the difference is merely relative. The USA had never even joined the Allies, merely subsidizing the sale of military hardware to them, and emerged as a sole "hyperpower" in the coming years.
Technologically, perhaps the biggest change was Teleforce turrets killing the aircraft carrier in its infancy. Theoretical exploration of quantum physics, combined with ideas from the meltdown weapons of the Blue Army, led the USA to call for greater transparency, with the Oversight Treaty of 1945 allowing the USA, the Allies, China, and Manchukuo to freely use designated high-altitude spyplanes on each other to watch for nuclear bomb tests. (They all monitored the balkanized "sovietlets" in the same manner.)
The late 1940s would see a series of "brushfire battles" between China and Manchukuo, which accomplished little, and eventually served as an embarassment before the West.
The Allies officially joined in the Alliance Of Europe in 1949, with a de-nazified Germany rising to economic leadership in the coming decades.
The early 1950s were a time of discovering the power of nuclear; rebuilding was powered by RTGs, NPUs, and later nuclear steam reactors. In 1952 the ESS published a closed-cycle solid-core nuclear rocket concept(Nerva); in 1955 the idea of nuclear bombs went public, and NACA published a nuclear pulse drive concept(Orion). The four great powers worked together and competed to explore space.
In 1956, the Pip Accords were signed, finally bringing peace to the heavily-balkanized remnants of the USSR. The Bratva organized crime bosses had become the de facto rulers, and formed a series of conglomerates; these were able to go legit, and in 1964 united to form the Spacey-Fillon Empire.
The late 1950s saw various cislunar missions using Nerva; Orion materialized in the early 1960s, supplanting Nerva in plans as the interplanetary drive of choice.
In 1965, the first interplanetary mission reached Mars, using one of the last Nerva mothership designs.
In 1970, an interplanetary mission reached Saturn, and toured its moons.