 Complete the following phrase:  Leading the advance from the north, the 9th Army ran into powerful Soviet defenses, and it gained no more than 10 km on the first day. Walter Model ordered the capture of the key and heavily fortified Ponyri railway station, which was needed to continue the advance towards Kursk. However, the Soviets had massively reinforced the towns defenses, which meant the attackers took very heavy losses. After a week of ferocious fighting, the 9th Army had gained just 20 km. After being unable to breach the enemy lines, the army was then forced 