I'm confident nothing will be lost.
Medieval Warfare
For Europe, the middle ages were very much a time of near continous warfare between nobles and local lords. The tactics and strategy of Ancient Rome were forgotten as it's empire was divided among the various barbarians who took it's land and religion. Warfare throughout the Middle Ages advanced by various developments, ranging from the stirrup to smelting. Most armies in the medieval world relied most heavily on their mounted soldiers. In Europe these were typically knights, but elsewhere camels and horse archers were also common. Archery was used, but achieved it's greatest significance after the development of the crossbow and mastery of the longbow by British marksmen. Medieval Warfare comes to a close with the development of gunpowder, which ushers in a new age of strategy.
Medieval Philosophy
Philosophy was in a different state in the Middle Ages than it was in the classical times of Ancient Greece and Rome. In a world where Monotheistic religion played perhaps the most important role in everything from daily life to international politics, much of the philosophy of the time was theologically oriented. Christian thinkers for years debated the nature of Jesus and Marie, with such controversies leading to the split between the Roman Church and Constantinople. Such philosophy was also present in the Muslim World, where discussion of ideas between educated minds was commonplace in Harun al Rashid's Baghdad.
Ballistics
To be completed later.
Gunpowder
Already included in Epic Game.
Medieval Sciences
Although European scientific advancement in the Middle Ages paled to it's latter golden age in the 16th century, it was certailny not nonexistent. Much of the Classical heritage and philosophy that fueled the Rennaissance was preserved in the middle ages. Since latin was the language of the church and the educated for years, the mathamatics of Euclid, the astronomy of ptolemy, and the works of Aristotle were all well known to late medieval scholars. Farther South in the Arab lands, philosophy and science had been thriving for centuries. Muslim scholars had made breakthroughs in Physics, Optics, Mathametics, and Medicines, even perfecting a system of Arabic Numerals that would go on to replace the old Roman system that was present in Europe at the time.