Turkish Cypriots had by now established an important bridgehead at Kokkina, provided with arms, volunteers and materials from Turkey and abroad. Seeing this incursion of foreign weapons and troops as a major threat, the Cypriot government invited George Grivas to return from Greece as commander of the Greek troops on the island and launch a major attack on the bridgehead. Turkey retaliated by dispatching its fighter jets to bomb Greek positions, causing Makarios to threaten an attack on every Turkish Cypriot village on the island if the bombings did not cease. The conflict had now drawn in Greece and Turkey, with both countries amassing troops on their Thracian borders. Efforts at mediation by Dean Acheson, a former U.S. Secretary of State, and UN-appointed mediator Galo Plaza had failed, all the while the division of the two communities becoming more apparent. Greek Cypriot forces were estimated at some 30,000, including the National Guard and the large contingent from Greece. Defending the Turkish Cypriot enclaves was a force of approximately 5,000 irregulars, led by a Turkish colonel, but lacking the equipment and organisation of the Greek forces.