There’s the history of judo that we’re all taught. Kano spent his childhood learning various forms of jujitsu and in the late 1870’s learns Tenjin Shinyo ryu jujitsu, followed by Kito ryu jujitsu, and in 1882 he founds the Kodokan. The styles that go in to judo, and even the dates around the history are really fuzzy. Andy Adams claims that “jujitsu was flourishing during Jigoro’s boyhood. One might even term the mid-19th century the golden age of jujitsu.” Conversely sources like Allen Gordon refer to jujitsu as a “dying art” at this time. And while Wikipedia indicates that Kano had difficulty finding a teacher, implying that his studies in jujitsu started around 1877, we have sources like Gordon noting an earlier relationship with Teinosuke Yagi who teaches Kano the “rudiments of jujitsu”.
Kazuzo Kudo gives us other clues that Kano’s jujitsu may have started even younger. He notes some of the same jujitsuka that the Wikipedia page references and the story meshes that no one will teach Kano all of jujitsu as he is too young. Kudo’s story and Gordon’s story seem at odds though. Gordon notes Yagi teaching Kano, while Kudo describes Yagi simply as being the man who points Kano toward Fukuda.
Fukuda is the point where we start seeing a consistent narrative. Kano trains Tenjin Shinyo ryu jujitsu under him for a number of years. Both Kudo and Adams note him dying in 1879, though Wikipedia seems to erroneously place this during 1880. It’s possible he falls ill in 1879 and passes in 1880, but it seems that Kano departs in 1879 to continue his training elsewhere. At this point all sources agree Kano went to continue his study of Tenjin Shinyo under Masatomo Iso. Where Fukuda emphasized randori, Iso emphasizes kata. Sources remain consistent that in 1881 Iso falls ill and Kano begins his study of Kito-ryu jujitsu under Tsunetoshi Iikubo. Iikubo, like Fukuda, emphasizes randori.
Fuzzy dates come up in a lot of the stories. I’ve always been told (and had found resources which noted) that Kano trained with Fukushima Kanekichi under Fukuda. Kudo tells us this is under Iikubo (though in the previous section you’ll note he dreams of kata-guruma while attaining his mastery of Tenjin Shinyo under Iso, a technique he had not yet discovered by this account). It doesn’t really matter which it is. We know it’s Fukushima who drives Kano to discover the technique. Though, this actually introduces another mystery as Kano is said to have searched out jujitsu because he was small and bullied, while the mythos surrounding kata guruma notes that Kano had previous experience in sumo and had turned first to those techniques before finding a book on western wrestling and adapting the fireman’s carry. I find it a bit odd because aside from this story I have trouble finding any history of the Kodokan that notes Kano had a sumo background.
The most finite date we come across in the history of judo is 1882. It is in February of that year that Kano opens his own school, the Kodokan. After this, things get fuzzy again.
Probably one of the oddest subjects is how judo gets its ground game. We tend to attribute it to Fusen ryu jujitsu, but the more I learn, the more I doubt that the style itself had a strong ground game. StackExchange had a solid answer to the question of Fusen ryu having a history of newaza. The TL;DR is – no. Fusen ryu seems to be a very typical koryu. It likely had an emphasis on standing joint locks, throws, and weaponry with the elements of ground work present, but by no means the focus. Rather, what we find is that Mataemon Tanabe was a great ground fighter and likely influenced a lot of the ground work of judo. DdlR of Bullshido’s post which the most complete answer draws upon is here. The TL;DR of it is exactly as expected – Tanabe was a beast on the ground, independent of Fusen ryu. What we do know from the continued tradition of Fusen ryu, which does still seem to exist and have schools, is that Tanabe was a master of it who taught it to others. In this way, similar to how people who train with me will learn unorthodox grips for throws, Fusen ryu probably did acquire a reasonably strong ground game due to Tanabe being in the lineage.
Probably the best person to ask about Tanabe is Tanabe. Luckily, he has a little autobiographical piece on his study of jujitsu that was translated to English. This is where we see that he had an explicit nickname of “Newaza Tanabe”. It also leads us to question if Tanabe ever ran a school, which would be required for the story I’ve always been told. It also implies that at some point Tanabe learned judo as he was a judo instructor at various places, and that at least of one of his students, Yuko Tani, was among the five men who traveled across the world to prove the efficacy of judo. The five men are Yuko Tani, Mitsuyo Maeda, Shinshiro Satake. Akitaro Ono, Taro Miyake. Their travels will result in some great mythos of their own, including the founding of Brazilian Jiu-Jitsu, but that’s a history for another day.
With any history it’s hard to say what really happened since at this point most of our sources are secondary or tertiary sources. We’ve been taught by oral tradition save a few dates committed to paper. What we can say is Kano definitely knew jujitsu, that at least Kito ryu and Tenjin Shinyo ryu found their way into judo, and that Tanabe was probably a strong driving force behind the newaza we know today. Everything else, well, I can say I don’t have any definitive answers.