{Being a Greek} (Hell(886e) (936e)). Concessive participle, though
he was a Greek. {Was compelled to be circumcised} ((886e)agkasth(880a)peritm(8874)h(886e)ai). First aorist passive indicative of anagkaz(935c)
and first aorist passive infinitive of peritemn(935c). Curiously
enough some scholars interpret this language to mean that Paul
voluntarily had Titus circumcised, instead of being compelled to
do it, an impossible view in my opinion in the light of verse  5 
and wholly inconsistent with the whole context. Paul means that
he stood his ground against compulsion and all force.