He found favour after his brother Theodore married into the imperial family, becoming the son-in-law of Emperor Alexios III Angelos.

[1] The Romans issued forth from the city, but were soon driven back to the gates, notwithstanding the stones that the defenders on the walls threw down onto the advancing Crusaders.

Laskaris refused to accept the imperial purple; escorted by the Patriarch of Constantinople, John X, to the Milion, he urged the assembled populace to resist the Latin invaders with all their strength.

Though his pleas to honour fell on deaf ears, they agreed to fight for increased wages,[2] and he marched out to make a final stand against the Latin Crusaders.

[2][4] The primary source for the elevation of Constantine Laskaris is Niketas Choniates, an eyewitness who recounted the fall of Constantinople to the Crusaders.

[8] Greek resistance to the Latin conquerors began almost immediately under the leadership of Theodore Laskaris, and he was soon joined by Constantine.

The last two fought with the Latin Empire against Theodore Laskaris' successor, John III Doukas Vatatzes, and were imprisoned and blinded.