If a knight or any other fighter killed an enemy in battle was it okay to take their armor and weapons?
Looting was not only okay, but an intrinsic and formally codified part of medieval warfare. Soldiers looted absolutely everything of value, both from slain enemies and from the unfortunate civilian population who happened to be in the way of marching forces. In the later medieval era, looting, plunder, and spoil were formally accounted for in a soldier's contract: he would recieve a certain share, another would be reserved for his captain, and the overall commander of the force would recieve another portion (the exact ratios and number of higher commanders taking a cut would vary). Soldiers looted partly to improve their own equipment (accounts of Agincourt say explicitly that English troops who did not have sufficient armor took the opportunity to loot armor from dead French soldiers), but primarily for their personal profit. The promise of pay far greater than normal military wages was a powerful motivation for soldiers to endure the hardship and risks that characterized a medieval campaign. Loot was not just limited to physical goods like equipment, jewelry, or wine, though. Capturing prisoners for ransom could also be extremely lucrative. The better known aspect of medieval ransoms are the more formal occasions when an important aristocrat was captured and held for enormous sums or political leverage . But common soldiers would also get in on the act by kidnapping local civilians near their camps and forcing their friends and family to pay up. This was not as lucrative as ransoming a king or prince but was far more accessible for the average soldier.