As was the case on the previous day, Warsaw Pact land forces started D+10 with incursions into Greek and Turkish territory in Thrace. The bulk of a Soviet motor-rifle division began moving into Turkish Thrace while two Bulgarian regiments (one motor rifle, one tank) advanced into Greek territory farther west. The amount of air and artillery support given to these incursions was respectable. But from the beginning it was apparent the Warsaw Pact effort was limited and did not signal the start of the long-awaited Pact offensive aimed at Istanbul and the Dardanelles.
Clashes took place along the length of the frontier, gradually moving deeper into the Thrace interior as the day went on. NATO forces were considerably more prepared then they had been the day before and it showed in their battlefield performance. In the east, Turkish forces blunted the Soviet push by the middle of the day. NATO air forces had also gained complete air superiority over the area by then as well. The combination of heavy casualties, stubborn Turkish armor to the front, and nearly incessant NATO air attacks compelled the Soviet commander to order a withdrawal at 1300. Additional losses were taken as combat units fell back to Bulgaria, and by 1700, Turkish Thrace was entirely cleared of Pact forces.
To the west in Greek Thrace, Bulgarian troops made unopposed initial advances down Motorway 1 towards Thessaloniki. The Hellenic Army was not encountered until the lead Bulgarian elements ran into a Greek mechanized infantry battalion setting up in a hasty defense outside of Nea Kavala. The Greeks were caught off guard yet stubbornly held their ground until additional units arrived. The battle expanded rapidly and by 1300, the two Bulgarian regiments and the bulk of the Greek 8th Infantry Division were locked in a battle that seesawed throughout the remainder of the day. As dusk settled, the Bulgarians started withdrawing back north towards the frontier. Both sides emerged from the fighting bloodied. The Bulgarians gained no ground, and endured high losses, yet learned a number of valuable lessons that could be applied later. The Hellenic Army’s baptism of fire also brought about heavy casualties, and lessons learned. However, the fact that the enemy had been driven from the field of battle and back across the border had a priceless effect on army, and national morale.
The simmering kettle that was the Socialist Federal Republic of Yugoslavia (SFRY) appeared to be dangerously close to boiling over. Discussions were being held in secret between officials from NATO, and the Croatian government amid a growing call for independence from Belgrade. Progress in the talks was slow, but events in Croatia and around Yugoslavia were threatening to overtake the covert diplomacy and force either NATO, or Belgrade’s hand. Ethnic tensions had been growing out of hand across the SFRY even before the war started. Yet the start of hostilities between NATO and the Warsaw Pact served as a gale-force wind that fanned the flames of ethnic tension.
Since 9 July, Yugoslavian President Slobodan Milosevic had been working feverishly to strengthen the central government, and keep the SFRY intact. His hopes for Soviet military assistance to clamp down on the more roguish socialist federal states had been dashed. It was clear now that the Soviets were not going to aid their Serbian brothers anytime soon. Time was running out, and on D+10 Milosevic realized action had to be taken.
Over the past three days a series of clashes between Croats and Serbs around Croatia highlighted the worsening situation in that particular region. With Milosevic’s blessing, Serbian nationalist groups were now operating in Croatia, in an attempt to strangle any move by Croatia to secede before it got past the embryonic stage.
In the afternoon of D+10 rumors of NATO-Croat talks reached Belgrade, prompting Milosevic to take stronger action. Following discussions with his defense council, Milosevic ordered the immediate movement of Yugoslav People’s Army forces into eastern Croatia, and preparations to begin for a larger commitment of forces in the coming days. In the late afternoon and early evening, Yugoslav Air Force MiG-21s began making low level flights over government buildings in Zagreb.
The message was clear. If Croatia did not fall into line on its own volition, Milosevic would take matters into his own hands.