figures, with one chronicler stating that the Mongols invaded with 500,000 troops. The Hungarians stopped to rest and to wait for additional supplies, but because of the wooded terrain on the far bank of the Sajó the king and the Hungarians still did not know that the main Mongol army was present. The cautious king ordered the building of a heavily fortified camp of wagons, a battle-tested countermeasure against nomadic armies. The Mongol plan It is highly unlikely that the Mongols originally wanted to cross a wide and dangerous river to attack a fortified camp. It is more likely that their original plan was to ambush the Hungarians while crossing the river, as in the Battle of the Kalka River, although this is still not certain. A Ruthenian slave of the Mongols escaped to the Hungarians and warned them that the Mongols intended a night attack over the bridge over the Sajó. The Mongols planned to bring their three contingents together if possible before engaging in battle and watched for signs that the Hungarians planned to attack. Though effective against traditional nomadic armies, the Hungarian camp became a liability due to the Mongols' advanced siege equipment. Fight at the Sajó bridge The Hungarians still did not believe that there would be a full-scale attack, but the troops of the King's brother Coloman, Duke of Slavonia, and Archbishop Ugrin Csák with Rembald de Voczon, the Templar master, left the camp to surprise the Mongols and defend the unguarded bridge. The Mongol force at the bridge was a vanguard sent by Batu to secure it during the night. They reached the bridge at midnight, having marched the last seven kilometres in darkness. When Coloman and Ugrin arrived they found the Mongols unprepared and in the middle of crossing the bridge. They successfully forced them into battle and achieved a victory there. The Mongols had been unprepared for the crossbowmen, who inflicted considerable losses on them, helped by the size of the bridge, which was at least 200 meters long. The Mongol vanguard was killed nearly to a man, with Thomas of Split writing: "the Hungarians immediately charged into them and did battle. They cut down a great many of them and pushed the rest back over the bridge, causing them to be drowned in the river." The Hungarians left some soldiers to guard the bridge and returned to the camp, unaware that