How to understand this passage “People are discovering new but often old identities …”

People are discovering new but often old identities and marching under new but often old flags which lead to wars with new but often old enemies.

written by Samuel P. Huntington in the book of ‘The Clash of Civilizations and the Remaking of World Order’.

The passage have a context, it gives an example : Protest marches of 70k people ( holding Mexican flags) was held in the opposition to Proposition 187 in L.A. on October 16, 1994. Some people raised a question “Why do they hold Mexican flags and request America offer free education to them, they should hold American flags”. After a few days, people changed to hold American flags and this ensured victory for Proposition 187.

I'm confused of the phrase ’new but often old ’ meaning. Is there something possibly be new but often old? Or it may refer to something like fossil or about archaeology, something is discovered and exposed recently but actually exists for a long time?

Like a friend who you have known long 【often OLD】, but one day you have an argument with him and then he becomes an 【NEW】 opponent to you? Does this accord with the meaning of “new but often old”?

I think he meant "new to the person adopting the identity". 'New' is often used this way, for instance someone may say "I just got a new car" when they mean that they have changed their 10-year-old car for an 8-year-old one. The 'new' car is far from being 'new' in the sense that it has just come from the factory but it is certainly a 'new' possession of the speaker and, hopefully, and improvement on the 'old' one.

You can also hear people referring to "new stock" when referring to an antique dealer or, sometimes, hear reference to "new exhibits" in a museum, even a geological or fossil collection when the exhibits are millions of years old but have only just been acquired.

A 'new but old' identity in that sense would be one which was a new one to the person taking on the identity but was drawn from the history of their place of residence, family history or ethnicity. For example the boxer Cassius Clay converted to Islam and took on a new Muslim identity calling himself Mohammed Ali partly because he believed that his ancestors who were enslaved in the 18th or 19th century would have been Muslims. Muslim identity is certainly not new but it was new to Ali. The same thing applies to Yusuf Islam who gave up musical success as Cat Stevens to become a Muslim.

Other 'new but old' identities would include those of early Cornish Nationalists who have taken on identities which would have been familiar to their ancestors but which are different from the British nationality with which most of them grew up.