The pop culture conception of Spartan generals tends more toward "bravery" than "brilliance," but Brasidas actually learned from his mistakes. He also focused more on achieving his goals than showing off. It wasn't enough to keep him alive, but there's a lot to learn from his example.

It's possible to be a strong, powerful, intelligent, effective leader and still fail at a long-term goal. The creations of even the most influential leaders eventually fade away. Zenobia did not achieve permanent independence from Rome, but she was an excellent political manipulator whose bold actions defied — and briefly founded — an empire.

This book review of The Emperor offers a glimpse into what a spectacularly corrupt medieval court might have been like. Halie Selassie ruled Ethiopia until 1974, and was incredibly up-front about his motivations when it came to exploiting the populace. Seeing the world through his eyes is uncomfortable, but educational.

Stable governments require clear succession rules, or the land devolves into civil war. Moctezuma I of the Aztec Empire managed to work out an effective system for stable inheritance, an impressive feat of negotiation in a land that used to be constantly destabilized by civil war.

After her husband the sultan died, former slave Shajar al-Durr took control of the country, defeated the Seventh Crusade, and took control of Egypt in her own right, and founded a dynasty that lasted 300 years. She was brilliant, ruthless, and ultimately brought down by the necessity of a bad compromise.

At the age of 25, Arminius of the Cherusci led several Germanic tribes in a battle known as "Rome's Greatest Defeat." He cleverly figured out a way to use Rome's strengths against them, and ultimately managed to wipe out 10% of their total military might. He was eventually killed by his own relatives.

It's possible for a leader to be too successful, especially when it comes to taxes. Aethelred 'the Unready' was an effective organizer with a motivated team of tax collectors. Unfortunately, he had to deal with Vikings.

Emperor Justinian and his wife Theodora have some of the coolest origin stories in Roman history. The folks at Extra Credits do a great job summarizing how they went from humble beginnings to being a pair of the world's most powerful — and competent — leaders. Sometimes, the best leadership is joint leadership.

Congratulations on making it all the way through this Deep Dive! I hope you learned something useful — or at least interesting — from these in-depth looks into different historical leaders. Many historical figures with great leadership skills and incredible vision were limited by the circumstances in which they found themselves. Some powerful, influential leaders were pretty horrible. They all have something to teach us.

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