On 1010.007M42 it did, but not in the way Imperial high command had anticipated. In the end, when the airdrop came, it came in low, and quietly from the sea. Rushing in from the North West, barely ten metres above the waves of the Great Melberg Ocean, fifty Mantas and over two hundred Barracudas unleashed a storm of firepower on the shoreline of Coravus, the Capital of the Isle of Cor.
The Tau had caught the Imperial defenders completely by surprise, having dropped from orbit on the other side of the planet and flying several thousand miles at wavetop height. This feat required extra fuel for the Mantas to carry, reducing the amount of troop carrying capability available, but the Cadres that landed quickly secured a beachhead.
These troops were followed by reinforcements carried by Orcas and soon the western portion of the city was under Tau control. Then, the Cora Defence Force under General Brooke launched a counter attack. Units of The Defence force attacked the Tau forces as they fanned out across the city. The firefight became an extended and confused affair with a great deal of inconclusive fire exchanged between the two forces. However by the end of the day the Tau had managed to partially encircle Brooke's men in the city and he was forced to abandon it to the Tau.
Meanwhile Jeffries' army charged towards the northern coast, attempting to secure the Hanibus straits before the Tau could. The hope was a forlorn one though, as when the first elements of Army Group North arrived, they could see Tau forces securing the port of Dechanel on the southern shore of the Isle of Cor. Infiltrating stealth units had sabotaged the docks during the night and low flying mantas delivered fire warriors to mop up once daybreak arrived. The port of Dechanel, Jeffries' last supply point, had been cut off.
The next few days allowed the Tau to mop up the remaining resistance within the confines of the Isle of Cor. The army of the Islanders, some 200,000 in total, surrendered when it found itself surrounded and unable to form a coherent defence. Now, Army Group North was surrounded in northern Narmala, and out of supply. The Imperial Navy, which had so far not intervened while the Tau took Cor from the air, now planned an airborne armada to resupply the trapped half a million men and their equipment, preparing them for their breakout.