 Complete the following phrase:  Meanwhile, Polish forces tried to move towards the Romanian Bridgehead area, still actively resisting the German invasion. From 17 to 20 September, Polish armies Kraków and Lublin were crippled at the Battle of Tomaszów Lubelski, the second-largest battle of the campaign. Lwów capitulated on 22 September because of the Soviet intervention; the city had been attacked by the Germans over a week earlier, and in the middle of the siege, the German troops handed operations over to their Soviet allies. Despite a series of intensifying German attacks, Warsaw, defended by quickly-reorganized retreating units, civilian volunteers and militias, held out until 28 September. The Modlin Fortress north of Warsaw capitulated on 29 September, after an intense 16-day battle. Some isolated Polish garrisons managed to hold their positions long after they had been surrounded by German forces. The enclave of Westerplatte s tiny garrison capitulated on 7 September and the Oksywie garrison held until 19 September; the Hel Fortified Area 