I think it is almost a cop out” to say the devil made me do it.
There is only 1 satan, he is not omnipresent. We are fully capable of sin without Satan’s involvement . Our fallen nature loves sin and it is very creative in ways to accomplish it .
Men love their sin .. it is not until we are saved that we begin to hate or sin and no longer be a slave to it..
Does he still “think” he can defeat God ...probably but saying that God and Satan are “locked in a battle ascribes to Satan powers and authority he does not have..we are not duelists that believe that there are two competing gods
God is also the God over Satan...
There has never been a question that there is only one God, and Satan does not reach his level of power, however the battle is at the soul by soul level, free will is in play both for Satan as the rest of creation, and he has influence as is told to us in the very words of the Bible itself.
That assertion is contradictory to the Gospels, which in several places speak of many devils. In one instance, the very name of the demons indicates a huge number.
I'd suggest re-reading the Gospels.
Some of these passages (in which Jesus or the Apostles cast out demons) are even used as Sunday Mass readings in the Catholic Church.