"...would hundreds of thousands of young Irishmen, all volunteers, have fought for Britain"

To suggest that that means they accepted Partition is an oversimplification, bordering on libel. It'd make my father spin in his grave. He fought as a Republican in the Civil War, and yet when the World War came, he joined the British Army. "I always believed in standing up for the rights of small countries, even my own" was the reason he gave when he was asked why. And he certainly came anywhere near accepting the partition of Ireland as justified.