Aside from the totality of the English victory, the death of “blind” King John of Bohemia upon the field is arguably the most well-known fact about the Battle of Crécy. According to the Italian chronicler Giovanni Villani, who had an interest in the career of the king who had so recently fought in Italian lands (on which, see Capponi's essay in this volume), John and his son Charles participated in the battle with an estimated contingent of 500 mounted Knights in heavy armor. In this context, we can assume that the whole Bohemian force, including foot soldiers and non-combatant servants, could have numbered up to 2,000 men, though it is notable that this contingent was not initially organized as a field army.

On July 11, 1346, the day before Edward III and his army landed in Normandy, Charles had been elected as the new Roman king by five votes. This close election precipitated a crisis between the supporters of Charles and those of the rival contender for the title, Holy Roman Emperor Louis IV of Bavaria. Yet even as he was gathering strength in Trier in order to fight Louis, Charles, very likely with his father, was called away to Vottem near Liège. The Bohemian forces were there in the moment of the battle on 19 July, when the Prince-Bishop of Liège, Engelbert de la Marck, fought against men-at-arms of Liège, but whether they took part in the military engagement — which was, in any case, a failure — is unknown. Charles (probably still with his father), then returned to Trier, where he was between 29 July and 4 August. They subsequently moved to Luxembourg, where they received messengers from King Philippe VI of France requesting their assistance against the English invasion. The Bohemian forces reached the French forces at Saint-Denis on or near 13 August.

Most of the armed forces that were with John and Charles at the start of August were thus designated as accompaniment for the trip to Germany for the expected crowning of Charles; King John and his son hastily reinforced this base with John's vassals from Luxembourg and several other Bohemian and German noblemen, but the combined force they brought to the aid of the French king was hardly formed as an army prepared for regular military expedition.