Thucydides began writing the history of which war when it broke out in 431 BC, and even served as a general in it?

A Briton named Cassivellaunus led the resistance to which Roman's invasion of Britain in the 50s BC? Which country's national anthem combines "Nkosi Sikelel' iAfrika" with "Die Stem van Suid-Afrika"? Which Ivan Turgenev novel, about the clash between two generations, popularized the word "nihilist"? On January 23, 1968, which country seized the USS Pueblo and detained its crew, accusing them of espionage? For his work developing nuclear-powered submarines, which admiral was known as the "Father of the Nuclear Navy"? Which singer co-wrote "Only the Lonely" and offered it to Elvis Presley before recording it himself? What is the name for the sun's crossing of the celestial equator, which happens twice a year? Which river flows more than 600 miles through Montana and Alberta before joining the Missouri?