Crusader. 15th Grand Master of the Knights Templar   [1] , 1219-1232.

A competent and experienced military commander, administrator, and politician, Pedro was made Grand Master of the Knights Templar   [1] on the Egyptian Nile, 28 January 1219, at a crucial point in the fifth Crusade. He remained Grand Master until his death in 1232, and as such he was in charge of the Christian defense of the Holy Land. He supervised the building of the largest Christian castle ever built in the Holy Land and played a key part in the politics of the sixth Crusade.

Howarth writes regarding his conduct during the fifth Crusade:

"Had they left the actual conduct of the Damietta Crusade to commanders ... who understood war... it would have turned out differently; but (Pope, ed.) Innocent, ... and (Cardinal, ed.) Pelagius all worked from the premise that the Prophet Mohammed must be the Great Beast of Revelations...

By the summer of 1219, the crusaders had advanced no further... Damietta ... had still not been taken.

In the pestilential heat of northern Egypt in August, a new Master was hastily elected: Pedro de Montaigu, a native of Aragon. ... a devout Christian, he was too seasoned a warrior to expect the easy fulfillment of a poorly-interpreted prophecy.

The Franks had an unexpected visitor, Francis of Assisi . The gentle saint paid a visit to the Sultan of Cairo... who (said, ed.) he would give them back the True Cross, Galilee, the whole of central Palestine, and Jerusalem as well... they turned it down.

Pelagius turned it down because he considered that no Christian should treat with an infidel. De Montaigu and the other military leaders, who were accustomed to doing so when it was expedient, also refused... for more practical reasons.... Guessing ... Egypt was possibly weaker than it appeared. ... in a shock attack Damietta was won at last. It was 5 November 1219; ...

... The Franks never penetrated more than another twenty miles up the Nile.

De Montaigu found in Pelagius none of the foresight that Honorius praised; instead there was nothing but blinkered folly. ... New overtures of peace came from the Sultan...

As brusquely as before, "a certain lord Legate" as de Montaigu called him, with withering sarcasm, refused. ... German reinforcements had arrived.

On 12 July 1221 Pelagius began the advance, blithely leading his men to their deaths. Six hundred and thirty ships sailed ... up the Nile. On the shore rode five thousand knights, with four thousand archers and forty thousand infantry...

... the Christians ... were surrounded and outnumbered. ... they attempted a retreat; at once the sluice-gates... were opened and the river flooded in. ... the Templars fought a desperate rearguard action.

"Our provisions were lost" de Montaigu wrote later to his brethren in England, "many men were swept into the stream, and we could make no progress. The water continued to rise, and we lost our horses and saddles and our baggage and everything that we had. We did not know where to turn, and being like fish caught in a net, we could do nothing but sue for peace."

... terms were merciful: all prisoners were to be exchanged... the Franks had only to quit Egypt and accept an eight-year truce. ... Pelagius and de Montaigu ... gave themselves up as hostages; ... on 8 September they ... sailed away..." (Howarth)

Pedro supervised the construction of "the most strongly fortified of all the places ever held by the Christians.", the castle 'Atlit, also known as Castle Pilgrim or Chastiau Pelerin. The leading quote is part of the name. The remains of Castle Pilgrim on the coast between Jaffa and Haifa, within sight of Mount Carmel, are the greatest monument to Templar Power in the Holy Land. It was never taken, and was only lost when the Templars evacuated the Holy Land in 1291. Castle Pilgrim could hold over 4000 people. It was attacked almost immediately by the Sultan of Damascus:

"The Sultan laid siege to the castle with sophisticated weapons... But the castle was well protected against the ...undermining of defense walls, since its foundations were under sea level. The garrison of 300 Templars, supervised by Pedro de Montaigu ... resisted all attack..." (Burman).

Pedro had to worry about his "allies" almost as much as his enemies, especially Holy Roman Emperor Frederick [1] :

"Frederick himself.... was half-German and half-Norman, but ... brought up in Sicily...

Frederick's Crusade arrived in Acre in September 1228. ... Frederick entered the Holy City... he crowned himself king of Jerusalem.

The fact was that nobody wanted a victory of that kind. It would... would be untenable... The Templars ... were furious.

... the Templars ... tried to entice the Sultan ... to murder him. ... Frederick threw a cordon of soldiers around the Templars house... threatening to kidnap... Pedro de Montaigu, ... The castle was far too heavily garrisoned for any such foolhardiness, and while Frederick remained in the Holy Land, de Montaigu was permanently surrounded by bodyguards." (Howarth).

I believe Pedro knew, and perhaps went to trouble to avoid, Pedro Guerin de Montagu, Master of the Hospital (Knights of Malta).

Sources:
The Knights Templar, Stephen Howarth.
The Templars: Knights of God, Edward Burman.

http://www.montaguemillennium.com/familyresearch/h_1232_pedro.htm