When Paul wrote Ephesians, he was writing to a church consisting of mostly Gentiles.
Stephen E. Fowl, in his commentary on Ephesians, goes further, saying, “Indeed, it does not seem that the Ephesian Christians have much, if any, direct contact with Jewish Christians.”
So Paul is writing in a context in which circumcision is not an issue. The distinction between Jew and Gentile is not an issue.
But Paul makes it an issue. He brings it up himself.
He does this after describing God’s grace, kindness, and power in saving them (Ephesians 2:1-10). He continues to stir up their appreciation of salvation by reminding them of their past.
First, read a redacted version of Ephesians 2:11-12. This is what Paul could have said to this church at this time:
“Therefore remember that you were once without Christ, having no hope and without God in the world.”
Now read the full version and see what Paul adds:
“Therefore remember that you, once Gentiles in the flesh—who are called Uncircumcision by what is called the Circumcision made in the flesh by hands— that at that time you were without Christ, being aliens from the commonwealth of Israel and strangers from the covenants of promise, having no hope and without God in the world.” (Ephesians 2:11-12, NKJV)
Paul is asking them to remember something about their past that they had never experienced in their past. Before their salvation, they may or may not have had a sense of alienation from God, but they certainly didn’t care about being alienated from “the commonwealth of Israel.” They didn’t think of themselves as “Gentiles.” That was only how Jews described non-Jews.
Here is Stephen E. Fowl, again, explaining that when Paul asked the church to remember their past, he was asking them to see it in a new way:
“Romans, Greeks, and other non-Jews in Ephesus (or elsewhere) would never refer to themselves as Gentiles. That designation only had currency within Judaism or in relation to Judaism. From the perspective of being in Christ, and as part of their remembering, Roman or Greek or Scythian Ephesians need to learn that they are Gentiles. They need to remember (or reconceive) of their past as a Gentile past. They need to learn both what being a Gentile meant when they were outside of Christ and what it means now that they are in Christ.”
Paul had just said, in Ephesians 2:10, that “we are His workmanship, created in Christ Jesus for good works, which God prepared beforehand that we should walk in them.” (NKJV)
Fowl sees this kind of remembering/reconceiving as an example of the works that God has prepared us for:
“…one of the primary good works that God has prepared beforehand for believers to walk in is the renewal, reconstruction, or repair of memory. This is so that both Ephesians and contemporary believers come to see their past (and their present and future) from the perspective of God’s saving activity.”
In his earlier letters, Paul was dealing with controversies regarding the relationship between Jews and Gentiles in the church.
Here in Ephesians, he has the opportunity to ignore that issue, yet he himself brings it up and spends significant time on it. If we want to have a full vision of God’s work in the world, we need to pay attention to what Paul goes on to say in Ephesians 2.
 Fowl, Stephen E., Ephesians: A Commentary (2012, Westminster John Knox Press)