Within this part, to avoid confusion because of the similarity of their names (Harold and Harald) Harold (King of England) will be referred to simply as Harold, and Harald (King of Norway) will be referred to by his last name, Hardraada.

Harold Receives of the News of the Viking Invasion
News of the attack on and burning of Scarborough was speedily brought to Harold who was in London.  The attack and burning of Scarborough occurred on Friday, 15 September 1066.  Messengers, riding their small English ponies, brought the news to Harold within four or five days. Therefore, by Tuesday, 19 September, or Wednesday, 20 September, Harold was aware of what had occurred at Scarborough.  The distance between Scarborough and London is approximately 200 miles, as the crow flies. The distance that the messengers had to ride must have been considerably longer, perhaps 250 miles, since they had to follow the roads and tracks. Therefore, the riders must have averaged 50 miles per day or as much 62.5 miles per day depending on whether it took them five days or four to reach London. Harold immediately recognized that this was not a hit-and-run Viking raid; it was an invasion.

Harold's Decision
Harold now had a difficult choice to make; whether to remain in the south or go north. Should he remain where he was until the weather window closed for a cross-Channel invasion, which is normally the end of September, or should he go north and settle matters with Hardraada and Tostig?

If he remained where he was, he would have to place confidence in the ability of Morcar and Edwin to defeat Hardraada and Tostig, or at least to hold them off until he could arrive with reinforcements. (It must be remembered that Harold was making this decision on the 19th or 20th of September, which would be the day before or the day of the battle of Fulford Gate.)

Harold decided to go north to settle the matter of the invasion at hand and then quickly return to the south to guard against William's threatened invasion. It is apparent from this decision that Harold was not aware that William was poised to sail, and the only thing that prevented him from doing so was the unfavorable wind. Possibly Harold had heard about William's fleet being mauled during the Channel storm of 12 September, which had destroyed much of his own fleet, or possibly he was placing too much faith in the weather, or possibly both. Whatever his reasons for doing so, Harold came to the conclusion that William's invasion would not be launched until mid-October and this would give him plenty of time to go up to Yorkshire, defeat Hardraada and Tostig, and return to the south to guard against William's invasion.

Harold Marches North
Therefore, on 20 September, the day of the battle of Gate Fulford, Harold and his army of 6,000 set out for Yorkshire. The army was predominantly Harold's Housecarls, who were aching for action, and anyone else who would volunteer or whom he could press into service. With the need for haste being paramount, Harold must have determined that his entire army must be mounted. The road distance to York was approximately 200 miles. On Sunday, 24 September, only four days after leaving London, the army rode into Tadcaster, which is about 10 miles south-west of York.  They had averaged an incredible 50 miles per day!

Harold Conceives His Plan of Attack
Tadcaster was situated very strategically for Harold. At this point, the Roman road that Harold had taken north was very close to the south bank of the Wharfe, only two miles from where Hardraada had left his fleet. Harold quickly learned of Morcar's defeat at Fulford Gate and the subsequent events at York. He knew that he could only depend upon the army he had brought with him from the south and any volunteers he could obtain from the immediate vicinity to attack Hardraada. He also knew; and this is extremely important, that his presence was unknown to the enemy. He immediately stationed guards at all entrances and exits to Tadcaster, and at other strategic points on the way to York; to Riccall on the Ouse, where Hardraada's fleet was moored; and to Ulleskill on the Wharfe, where a small flotilla of Morcar's was.  Therefore, secure in the knowledge that his presence in the area was unknown and that he had taken all necessary precautions to keep it that way, he allowed his army to rest and recuperate in the meadows around Tadcaster and continued to gather intelligence.

The collection of intelligence was swift. Harold was quickly informed of Morcar's defeat at Fulford Gate. Morcar's sailors, whose flotilla was moored at Ulleskill, informed him that Hardraada and Tostig, and their entire army, had left York and returned to their fleet at Riccall. People who had been in York when it surrendered to Hardraada acquainted him with the terms of the surrender, which included the most important information regarding the meeting that was to take place at Stamford Bridge the next day for the transfer of the 100 hostages into Hardraada's hands.

Based upon the information he received, Harold decided that his best course of action was to go to York early the next morning, reestablish his authority there, and then take his army to Stamford Bridge, where his sudden and unexpected appearance would catch Hardraada and Tostig off guard. He ruled out an attack on Riccall because he might not be able to achieve a complete surprise due to Viking sentries that were sure to be posted and who would give warning to the main body; thus, the complete victory that he desired would elude him. He also thought about a surprise flank attack on the Vikings as they were approaching Stamford Bridge, which, on the face it, seems very appealing; however, he reasoned that since they were expecting to be going to a peaceful meeting they would be strung out over a great distance and a surprise attack on their flank would therefore not accomplish much. The course of action that he chose to take would catch the enemy totally by surprise and unprepared for combat.

Harold Enters York
According to one edition of the Anglo-Saxon Chronicle, Harold and his army departed Tadcaster on Monday morning, 25 September and rode the 10 miles to York. According to the Norwegian scribe Snorri, they left Tadcaster and entered York on the night of the 24th. There is no other evidence one way or the other and it probably doesn't matter much. It is certain that he arrived very early in the morning because he needed time to settle matters in York and then get to Stamford Bridge before the meeting was to take place.

Harold Marches on Stamford Bridge
Therefore, before the morning was far advanced, Harold proceeded to Stamford Bridge, which was only about eight miles away to the north-east. Harold's army kept to the Roman road for the first seven miles, then halted at Helmsley Gate, just out of sight of Stamford Bridge, which was visible from the road just ahead of them, and waited there as the Vikings leisurely arrived for the meeting. Harold watched as the Vikings assembled in groups on both sides of the bridge, which spanned the river Derwent. When he determined the time was right, Harold ordered his Housecarls and fyrdmen forward.

The Battle
As Harold's army came over the rise on the hill and the sun reflected off their shields, the Vikings were stunned. The complete surprise desired by Harold was achieved. The Vikings were caught with their force divided; the smaller part being on the northern end of the bridge with the English bearing down on them, and the larger part on the southern end. To make matters worse, because the day was so hot and combat was not expected, Hardraada had allowed his men to leave their armor behind at Riccall, which is what most of them did. Still worse was the fact that he had only brought two-thirds of his army with him, leaving one-third behind at Riccall to guard the fleet. Lastly, Hardraada did not know the lay of the land and had no plan in mind because he had not expected a battle. Taking all this into account, Tostig, who was well acquainted with the area and knew his brother's fighting capabilities first-hand, urged Hardraada not to accept battle but to immediately retreat as quickly as possible back to Riccall. Hardraada considered this but decided to give battle because he knew that, if he retreated, Harold's Housecarls would surely close in upon his flank and rear before long and he also reasoned that Harold would have sent a small force ahead to Kexby, to secure the essential crossing of the Derwent at that place, thereby blocking any further retreat to Riccall.

Deciding to accept battle, Hardraada quickly dispatched a messenger back to the commander of the contingent he had left behind at Riccall, Eystein Orre, ordering him to bring up the other third of the army to Stamford Bridge as quickly as possible. Then, he quickly evacuated most of his men who were on the north bank; that is, the same side of the river on which the English were approaching, to the south bank, leaving a small rear-guard there to block the bridge.  Hardraada and Tostig had just enough time to form their best armed men into a line of defense along a ridge about 300 yards south-east of the Derwent.

The rear-guard at the bridge could not hope to hold out long against the English and were quickly overwhelmed. Once over the bridge, the English, according to custom, formed themselves into a long line several ranks deep, facing the enemy which was deployed along the ridge above them. After his entire army had crossed the bridge and deployed into the line, Harold ordered them forward. Although the fighting was fierce, the lightly armed and armored Vikings stood no chance against Harold's Housecarls and were quickly destroyed. Hardraada was mortally wounded early in the combat and died before it ended. Later on, Tostig was also killed. Even though both of their leaders were killed, the Vikings, who were now fighting in small groups, were still defending themselves valorously when Eystein Orre arrived with the reinforcements. However, these troops proved to be of no assistance because the forced march they had been compelled to make on this unusually hot day had spent their energy and they, too, were quickly overwhelmed. Eystein Orre was killed late in the day.

The Results of the Battle
The Battle of Stamford Bridge was a resounding victory for Harold and an overwhelming defeat for the Norwegians. The Vikings who survived the battle straggled back to Riccall under hot pursuit of the English. There was a last-gasp defense at the fleet but this was quickly ended and the surviving Vikings capitulated to Harold. Desiring total victory but not maddened with blood-lust to kill all the enemy, Harold rounded up all the surviving Vikings and let them go. There were only enough of them to man 24 ships. They were also permitted to take all of their dead with them, to include the body of Hardraada, but not Tostig's.