The question arises – why should it be carried openly? It is “out of love for the precept” – that is to make clear that fulfilling the laws of circumcision override the laws of Shabbat.
And the “times of danger” were real – when circumcision was outlawed as one of the means to destroy the Jewish people (i.e. before the Maccabean revolt and in the Hadriatic persecution). Even in those times, circumcision continued – but surreptitiously and at danger.
These acts of defiance are noted and celebrated. For example, this story is told about someone who was called “Elisha-the-man-of-the-wings”
And why is he called 'the man-of-the-wings'? Because the wicked State(Rome) once proclaimed a decree against Israel that whoever donned tefillin should have his brains pierced through; yet Elisha put them on and went out into the streets. A quaestor (Roman officer) saw him: he fled before him, and the latter gave pursuit. As he overtook him, he [Elisha] removed (the tefillin) from his head and held them in his hand, 'What is that in your hand?' he demanded, 'The wings of a dove,' was his reply. He stretched out his hand and the wings of a dove were found therein. Hence he is called 'Elisha-the-man-of-the-wings.'
And why did he tell him the wings of a dove rather than that of other birds? Because the Congregation of Israel is likened to a dove, as it is said, as the wings of a dove covered with silver, and her pinions with yellow gold (Ps. 68:14) just as a dove is protected by its wings, so with the Israelites, their precepts protect them.