The French lost the campaign because they could not secure their lines of supply and keep their men fed and supplied. Their failure to win the final battle at Murca
Allowed Wellington to force a draw. The lack of supplies meant the French were unable to maintain their positon and they had to retreat.
The Oporto campaign was the fourth phase in Northern Spain between the Fourth French and the Anglo Portuguese armies. It lasted 7 days and there were three battles. The British won two and the French one.
The British won the Oporto campaign phase
The campaign started on 1 March and ended on 22 May 2016