He was governing the viceregal at the time of the defeat of British Admiral Edward Vernon at the Battle of Cartagena de Indias.
In 1740 New Granada was reestablished as a viceroyalty, for the same reasons as it had originally been established — large distances, growing population, tax collection, defense, and administrative control.
In August 1739 Sebastián de Eslava was named the first viceroy of this second incarnation, with express instructions from the Crown to defend the viceregal against British attacks.
On November 21, 1739 British Admiral Edward Vernon captured Portobelo, on the Atlantic side of the Isthmus of Panama, which was part of the new Viceroyalty.
On March 13, 1741 he blockaded the port with 51 warships,[1] 135 transports, 2,000 cannon and more than 28,000 men, possibly the strongest fleet ever assembled up to this time.
On the night of April 19, as part of the battle of Cartagena de Indias, the British began a major assault on the wall of the fort of San Felipe.
During his administration, Viceroy Eslava founded hospitals and towns, constructed roads, promoted the pacification of the Motilones Indians, and contributed arms, money and provisions to defend some cities (like Pamplona and San Faustino), and to maintain navigation on the Zulia River.
After his return to Spain, King Ferdinand VI named him captain general of Andalucia, and later, on July 2, 1754, minister of war.