The painting illustrates the exchange of keys that occurred three days after the capitulation between Spain and the Netherlands was signed on June 5, 1625.
Hence, the focus of the painting is not on the battle itself, but rather the reconciliation.
At the center of the painting, literally and figuratively, is the key given to Ambrogio Spinola by Justin of Nassau.
This battle painting is notable for its static and sentimental qualities, as Velázquez left out the blood and gore that would normally be linked to the violence of such battles.

According to the statement made by eye-witnesses, both [Spinola and Nassau] had dismounted and Spinola awaited the arrival of Justin surrounded by a “crown” of princes and officers of high birth.
The governor then presented himself with his family, kinsfolk and distinguished students of the military academy, who had been shut up in the place during the siege.
Spinola greeted and embraced his vanquished opponent with a kindly expression and still more kindly words, in which praised the courage and endurance of the protracted defense.

The extraordinary respect and dignity Spinola demonstrated towards the Dutch army is praised through The Surrender of Breda.
Spinola “had forbidden his troops to jeer at, or otherwise abuse the vanquished Dutch, and, according to a contemporary report, he himself saluted Justin.”
The painting demonstrates the glimpses of humanity that can be exposed as a result of the war and commends Spinola's consideration for Nassau and the Dutch army.

Velázquez's relationship with Spinola makes The Surrender of Breda especially historically accurate.
The depiction of Spinola is undoubtedly accurate, and Spinola's memory of the battle contributed to the perspective with which Velázquez composed the painting.
Velázquez “desired in his modest way to raise a monument to one of the most humane captains of the day, by giving permanence to his true figure in a manner of which he alone had the secret.”
The painting illustrates the exchange of keys that occurred three days after the capitulation between Spain and the Netherlands was signed on June 5, 1625. Hence, the focus of the painting is not on the battle itself, but rather the reconciliation. At the center of the painting, literally and figuratively, is the key given to Ambrogio Spinola by Justin of Nassau. This battle painting is notable for its static and sentimental qualities, as Velázquez left out the blood and gore that would normally be linked to the violence of such battles.
According to the statement made by eye-witnesses, both [Spinola and Nassau] had dismounted and Spinola awaited the arrival of Justin surrounded by a “crown” of princes and officers of high birth. The governor then presented himself with his family, kinsfolk and distinguished students of the military academy, who had been shut up in the place during the siege. Spinola greeted and embraced his vanquished opponent with a kindly expression and still more kindly words, in which praised the courage and endurance of the protracted defense. 
The extraordinary respect and dignity Spinola demonstrated towards the Dutch army is praised through The Surrender of Breda. Spinola “had forbidden his troops to jeer at, or otherwise abuse the vanquished Dutch, and, according to a contemporary report, he himself saluted Justin.” The painting demonstrates the glimpses of humanity that can be exposed as a result of the war and commends Spinola's consideration for Nassau and the Dutch army.
Velázquez's relationship with Spinola makes The Surrender of Breda especially historically accurate. The depiction of Spinola is undoubtedly accurate, and Spinola's memory of the battle contributed to the perspective with which Velázquez composed the painting. Velázquez “desired in his modest way to raise a monument to one of the most humane captains of the day, by giving permanence to his true figure in a manner of which he alone had the secret.”
The Surrender of Breda