In 2015 he graduated from University College London with a PhD, where he was supervised by Professor Hans van Wees.
[11][12][13] His research challenges the so-called "California School" of Greek military scholarship, arguing that its theories were largely based on outdated 19th-century models.
[17][18][19] With Cezary Kucewicz and Matthew Lloyd he edited Companion to Greek Land Warfare Beyond the Phalanx (2021), and also wrote three chapters of it.
[20] He published his second monograph, Between Miltiades and Moltke: Early German Studies in Greek Military History, in 2022.
[21] In September 2022, Konijnendijk was appointed Darby Fellow and Tutor in Ancient History at Lincoln College, Oxford.