[AntiGuv]

Just because you say it doesn't make it true. Where did you read it? I'm suspicious of historians because they often did not agree and don't know which ones are credible.

You can read about it all over the internet, but I assume you will find the Jewish Encyclopedia most credible of all:

In order to prevent the obliteration of the "seal of the covenant" on the flesh, as circumcision was henceforth called, the Rabbis, probably after the war of Bar Kokba (see Yeb. l.c.; Gen. R. xlvi.), instituted the "peri'ah" (the laying bare of the glans), without which circumcision was declared to be of no value (Shab. xxx. 6).

The "peri'ah" is the radical circumcision as we know it today, as opposed to just snipping the tip which was the custom prior to the Bar Kokhba revolt (132-135 AD).

[Aliska]

I would tend to find that credible. Because of the conflicts between the two religions, some of their later writings I would not, as some writings in my chosen religion are not credible, to me anyway.