Based on your interest in Tacitus and Thucydides, I might recommend the The Histories of Polybius. [1] It is absolutely mind-blowing to me that he actually witnessed the events he writes about, and how analogous it is to modern-day geopolitics.

By the way, thank you for providing your list of books - I picked up a few future reads from it.

1. https://www.gutenberg.org/files/44125/44125-h/44125-h.htm