Glele continued his father's successful war campaigns, in part to avenge his father's death, in part to capture slaves. Glele also signed treaties with the French, who had previously acquired a concession in Proto-Novo from its king. The French were successful in negotiating with Glele and receiving a grant for a customs and commerce concession in Cotonou during his reign. Glele resisted English diplomatic overtures, however, distrusting their manners and noting that they were much more activist in their opposition to the slave trade: though revolutionary France itself had outlawed slavery at the end of the 1700s it allowed the trade to continue elsewhere; Great Britain outlawed slavery in the U.K and in its overseas possessions in 1812, and had its navy make raids against slavers along the West African coast starting in 1840.
Glele, despite the formal end of the slave trade and its interdiction by the Europeans and New World powers, continued slavery as a domestic institution: his fields were primarily cared for by slaves, and slaves became a major source of 'messengers to the ancestors' (sacrificial victims) in ceremonies.
Near the end of Glele's reign, relations with France deteriorated due to Cotonou's growing commercial influence and differences of interpretation between Dahomey and France regarding the extent and terms of the Cotonou concession grant. Glele, already on his death bed, had his son Prince Kondo take charge of negotiations with the French.