Similar to the Alps, the Pyrenees were a natural danger that separated France and Spain, not only preventing the Moors of the Umayyad dynasty from conquering the Kingdom of France hundreds of years ago, but also preventing the Carolingian ancestor Charlemagne, Charlemagne's grandfather and Prime Minister of France, from conquering the Catalans of Barcelona.

Because of the steep Alpine mountains, there are only two narrow land routes between France and Spain, one of which is the Pyrenees, the part of the area from the Atlantic coast to the Somport Pass, where most of the peaks are less than 1,800 meters above sea level, and there are many natural mountain passes formed by river erosion, which are natural passages between the two countries.

The other is the area from the Eastern Pyrenees to the Mediterranean, which has a low altitude, especially about 48 kilometers from the Mediterranean, and has a mountain pass with an altitude of 300 meters, which is the main road to the north and south.

Of the two passages, the eastern passage connecting Barcelona and Toulouse is relatively safe in the possession of William, while the other western passage connecting Gascony with Castille and Navarre is much more dangerous.

On the one hand, it was closer to the core of Castile, and if William tried to force his way through it, he would inevitably be thwarted by Sancho and the Castiles, and would suffer heavy casualties, which William did not want.

Fortunately, the control of the sea in the Atlantic had already been controlled by William and the Norman navy, and he planned to use the three legions led by Duke Rodrigo as bait to attract the attention of the other party at the Sibilenees Pass, while he himself led his two Guards Corps and the Nordic Guard to land in Biscay from the Bay of Biscay.

If everything goes as planned, William, with the help of Earl Eneco of Biscay, will land in the rear of Sancho's main force and flank Sancho's main force together with Duke Rodrigo, who has broken through head-on.

Faced with as many as twice as many troops, no matter how brave King Sancho and the knights of Castille were, they would not be able to win.

"What if the people of Castille were not fooled, but instead retreated between the hill castles of Burgos or León?" Rodrigo offered his opinion.

"Then it is safe and steady, if there is no main force of the enemy to stop the Pyrenees Pass, how can we prevent our army from breaking through this natural danger?

You must know that they are facing an empire, a huge empire that combines France, Normandy, England, Rhineland and Italy, and they will never be able to win in the competition of strength! The corners of William's mouth curled slightly, and his tone was firmly convinced.

"Your Majesty, Henry IV of the Holy Roman Empire has just taken over the throne now, this man is ambitious, not a peaceful fellow, is it too rash to transfer the Third Legion out of the Rhineland." Duke Richard spoke up.

Duke Richard was sorry that he was unable to participate in the war due to his health, but he still managed to attend the military meeting and provide William with his own advice.

"What Duke Richard said is not unreasonable, this battle can be said to have dispatched most of the elite of the empire, including six standing legions, two guards legions, and two legions stationed in Italy, only with two newly formed legions to defend the border, the defense is indeed a little weak." William stroked the beard on his chin slightly and groaned.

"Your Majesty, it is better to transfer the Fourth Legion to Brussels to defend the Rhine and the HRE border, and I believe that with the Duke of Richard personally leading the Fourth Legion and the other two legions, it will be enough to ensure the safety of our borders." Rodrigo stepped forward and proposed.

"What do you think, Lord Richard?" William nodded slightly, turned his head to look at Duke Richard and asked.

"Since Your Majesty orders, the old minister obeys the order." Duke Richard thought that his body was decrepit, and he was afraid that he would not have any chance to perform, but he did not expect that there would be a place to use him, so he readily agreed.

"With Duke Richard in charge, I can also feel a little more at ease here." William smiled and nodded, then looked at Rodrigo and Duke Andrew and said:

"Lord Rodrigo, your side has transferred the main Fourth Legion, and it tends to be weak in terms of troops, and I am worried that the number of troops is too small to succeed in attracting Sancho's attention.

In this case, I will drop a legion from Duke Andrew's side to support your western front.

Duke Andrew, Duke Rodrigo, what do you two think? ”

"It's all at Your Majesty's command."

Although Duke Andrew's side is a little reluctant, he is not an unreasonable person, he knows very well that the key to this battle is whether Duke Rodrigo's side can attract Sancho's attention or break through the Pyrenees Pass, while his side is mainly threatening the enemy's flank and distracting the enemy's forces, and in terms of strategic importance, his role is weaker than that of Duke Rodrigo's.

"That's it, my lords, hurry up and prepare, and when the whole army is assembled, you can start it!"

Seeing that Rodrigo was about to speak and stopped, William did not give the other party a chance to speak, and immediately issued a final order.

William was well aware of Rodrigo's personality and integrity, but he was sometimes a bit rigid, especially easy to be more serious, and he felt guilty that he had lost a legion under Duke Andrew's command because of his proposal.

If William had given him a moment to plead, the boring military agreement would have been prolonged indefinitely.

......

This expedition to Spain naturally relied on the help of the two great French rivers of the Loire and the Garonne, without which they could not carry baggage and soldiers, and with the current land transportation situation, it would not be possible to afford the supply of up to 80,000 troops.

Fortunately, in this war to conquer Castile and Leon, William deliberately divided the army into three units, each of which numbered about 30,000 people, of which William himself could rely on sea transportation to support, Rodrigo had the Garonne River system to carry baggage, and Andrew's side could rely on the prosperous Mediterranean trade to obtain supplies nearby, so William did not have to worry about the lack of supplies in the war.

As William gathered his army and marched to Spain to launch a conquest, it seemed that the whole of Europe was also in an inexplicable frenzy, and the princes and monarchs were fighting one after another, and the original atmosphere of peace suddenly disappeared.

Of course, they didn't point the finger at William, and of course they didn't dare to provoke William.

The reason why they were so restless this time was naturally because the pressure that oppressed them disappeared after William came out, especially in the Holy Roman Empire, where the newly appointed Henry IV ambitiously pointed the finger at the princes who had committed rebellion, especially the Dukes of Savoy, Swabia, and Carinthia.