You specified the empire of "Russ" so I assumed you meant the Russians in the same location as OTL Russia.
Hoovertanks?
Hoover is the brand name of a vacuum cleaner, which would be an interesting concept for warfare

but I'm not sure that's what you mean. I found a site for a Hover Tank game.
Unholy
This can mean not sacred, sinful or dreadful. It doesn't necessarily have to mean diabolic or demonic. So it wouldn't take much for "Unholy" to mean "Secular".
But this would take such an early POD, the word might be butterflied out of existence, but other words might take its place, like a hypothetical Old Norse "Unhalik", let's say.
In other threads folks have said, the location of Rome was such a good spot, some city would have been built there in just about any timeline.
Suppose this alternate Roman empire splits in two, half theocratic and half secular, and the secular part is known by English speakers as "unholy", meaning secular, not a theocracy--but not necessarily diabolical.
The other half of the empire is known by many names, including "Holy Roman Empire." But it's not necessarily any worse than OTL Holy Roman Empire.
Kamikazis
That's a familiar Japanese idea. The word first referred to the typhoons which thwarted the Mongol invasions of Japan ca. 1280.
So around 200 BC-200 AD, instead of the Koreans invading Japan...a plague wipes out a lot of Koreans, and civil war induces many Japanese to invade Korea. They go on from there to invade China during a Chinese civil war.
That would change the language, and the word "kamikazi" might be different, but the concept might remain--the idea of a Japanese army or individual soldier being compared to a typhoon. Later, they might have the idea of suicide attacks as well.
A Chinese genius invents hot air balloons, which are later developed into dirigibles.
Kali-worship
Around this time, Tibet was strong and expansionistic. Instead of Buddhist monks, Hindu monks establish Hinduism in Tibet. During another round of Chinese Civil Wars, Tibetan followers of Kali invade China and introduce Kali worship there. One of the many nomadic Asian tribes takes on Kali worship and one of their leaders becomes like Genghis Khan.
This tribe was hardly known in OTL, but they become like the Mongols, only a thousand years earlier. They invade and conquer all across Asia and Europe, spreading the idea of Kali-kamikazes. The precursors of the Russians don't take to Kali worship but they do like the kamikazi idea.
They're the ones who start using dirigibles in their battles. Members of one clan of the tribe hold the secret. There are enough people who know, so it's not forgotten; but the secret is tightly held, so it is hundreds of years before another genius figures out the secret on his own.
This tribe continues to Scandinavia, and finally settles down into relative quiet. But the Kali worship continues to spread, south into the British Isles, where the Vikings pick it up ca. 500 AD, just when they're about to begin ravaging Europe...