Circumcision or not

I was reading the Bible yesterday and I had a few questions. I thought I would open it up to all of you to get your thoughts and opinions. Possibly, they can be backed by some sort of relevance.

In Acts Chapter 15 certain men taught that "Unless you are circumcised according to the custom of Moses, you cannot be saved." So Paul and Barnabas went to Jerusalem to discuss this with the elders. Paul and Barnabas reported many wonderful things that God has done with the Gentiles. But some of the believers still thought that they should be circumcised and keep the commands of Moses. Finally Peter spoke up and spoke of how God wanted the Gentiles to experience his Holy Spirit just as the Jews did, making no distinction between them. Peter said that through the grace of the Lord Jesus Christ we shall be saved in the same manner. James added that the prophesy of Amos 9:11,12 had been fulfilled, and that we should not have them become circumcised but rather have them be free from sin like sexual immorality.

So they wrote a letter that Paul, Barnabas, Judas, and Silas delivered to the Gentiles at Antioch, Syria, and Cilicia stating these things. When the churches received the letter they rejoiced with encouragement. At the end of Chapter 15 Paul and Barnabas get into an argument and part ways. Silas goes with Paul to Lystra where he meets Timothy at the beginning of chapter 16. Timothy was the son of a Jewish woman who believed in Jesus but his father was Greek. Paul wanted to take Timothy with him on his missionary adventures. Verse 3 of Chapter 16 is confusing me. Here it goes: ... And he took him and circumcised him because of the Jews who were in that region, for they all knew that his father was Greek. Verse 4 continues... And as they went through the cities, they delivered to them the decrees to keep, which were determined by the apostles and elders at Jerusalem.

Now wait a minute. Didn't the elders at Jerusalem decide not to require circumcision? Yet Timothy was taken by Paul to be circumcised. He did this for a reason, but wouldn't it be a great opportunity for him to explain why Timothy didn't have to be circumcised, because of the grace of our Lord Jesus Christ.

Peter was quoted back in Jerusalem (Acts 15:10) saying "why do you test God by putting a yoke on the neck of the disciples which neither our fathers nor we were able to bear?" He is referring to the requirement of circumcision.

Paul probably had good reason for having Timothy circumcised, but I am unclear on what that exactly is.

Thanks for your thoughts.