Since quite a few of you have questions about the timeline and feel it differs from what you had in mind, I've dedicated this standalone chapter to explaining it.
First, Baidu Baike isn't necessarily entirely accurate. Its entries were written by people, too, and many were written very early on. They weren't necessarily updated after official Naruto explanations came out later.
You've read the original manga or watched the anime and formed your own interpretations, or looked things up on Baidu Baike and immediately been steered toward certain ideas.
But really, since we authors are writing fanfiction, how could we possibly skimp on studying and examining the manga?
I wouldn't dare start writing after reading the manga just once.
I've studied the manga and anime at least four or five times, and I've also read all the various official reference books, including the Rin, Pyō, Tō, Sha, Kai, and Jin books, and so on.
I basically keep the Baidu Baike reference pages open as I write.
We authors aren't going to deliberately create plot holes. All we think about is how to reduce them.
But the original itself has some plot holes that can't be explained... I won't go into those here.
What follows is the summary and interpretation I arrived at after studying the manga many times, writing three Naruto fanfics, and consulting reference material countless times.
It may not match Kishimoto's intentions perfectly, but I at least think this is the most reasonable interpretation and the closest to the original. Otherwise, a lot of things simply can't be explained, and even more plot holes crop up.
Simply put, this is a timeline summary with the fewest plot holes.
Some people think the First Hokage died during the First Shinobi World War.
That clearly couldn't have happened.
The First Hokage brought peace to a chaotic era and became the God of Shinobi. There were no wars while he was alive. Which of the other four great shinobi villages would have dared start one?
What? You're saying Madara Uchiha helped the other shinobi villages attack Konoha, and that was how the First Shinobi World War started?
If Madara Uchiha joined forces with other villages, he wouldn't be Madara Uchiha.
So, after Madara Uchiha fought the First Hokage at the Valley of the End, the First Shinobi World War didn't break out until the First Hokage died.
Only after the First Hokage died did the other shinobi villages dare launch a Shinobi World War.
During the First Shinobi World War, the Second Mizukage and Second Tsuchikage fought each other and both died.
Toward the end of the First Shinobi World War, the Second Raikage and Second Hokage Tobirama Senju wanted to negotiate peace, but Kinkaku and Ginkaku ambushed them, resulting in both their deaths.
Of course, there may be questions here, too. Perhaps Tobirama Senju didn't die immediately, but was gravely wounded and held on for a few more years before dying. However, there's no definitive account, and the original never indicated this either.
Next came the Second Shinobi World War.
In the Second Shinobi World War, the Three Great Shinobi Villages first fought a major war in the Land of Rain. It lasted a year and ended with the Sannin making their name.
Konoha's White Fang also made his name during this period. Konoha's White Fang was older than the Sannin and was their senior. Official sources stated that Konoha's White Fang was someone even the Sannin had to respect.
After that came the closing phase of the Second Shinobi World War, which lasted several years. It was an extremely protracted series of localized conflicts, with the great shinobi villages fighting one another while also forming alliances with one another. In short, one word summed it up: chaos.
In the end, Konoha could be considered the biggest victor. It plundered enough resources and built up enough of an advantage to lay the groundwork for fighting four opponents alone in the Third Shinobi World War.
In the Third Shinobi World War, the four great shinobi villages joined forces to attack Konoha. By then, Konoha's Orochimaru, Tsunade, and Jiraiya had all matured. All were Kage level, and each could hold a front alone. Together with Hiruzen Sarutobi in his prime, they withstood the combined assault of the four great shinobi villages.
But they didn't break the stalemate.
The one who broke the stalemate was Minato Namikaze.
The Third Shinobi World War was the war in which Minato Namikaze made his name. Minato Namikaze swept across the entire war's battlefields single-handedly, helping Konoha gain the advantage on essentially every front. The Yellow Flash's name resounded throughout the Shinobi World.
The Second Shinobi World War was incredibly exciting, and the Third Shinobi World War was even more so.
There was Konoha's White Fang, whose Hatake Kenjutsu stood unrivaled in the Shinobi World, and there were the Sannin fighting the Demigod, Hanzo of the Salamander.
Then there was Might Duy opening the Eight Gates and thrashing the Seven Ninja Swordsmen of the Mist, Minato Namikaze sweeping the battlefield with Flying Thunder God, the Third Raikage fighting ten thousand enemies alone for three days and three nights, Body Flicker Shisui making his name on the Kirigakure battlefield, and so on and so forth.
Just talking about it gets my blood pumping. I hope I can write an exciting Shinobi World War for you all, and I hope you'll give me your support.