from Kraków. He led a better-organized and reinforced ground attack. The longest-lasting defense of a position took place around the ŻZW stronghold at Muranowski Square, where the ŻZW chief leader, Dawid Moryc Apfelbaum, was killed in combat. On the afternoon of 19 April, a symbolic event took place when two boys climbed up on the roof of a building on the square and raised two flags, the red-and-white Polish flag and the blue-and-white banner of the ŻZW. These flags remained there, highly visible from the Warsaw streets, for four days. During this fight on 22 April, SS officer Hans Dehmke was killed when gunfire detonated a hand grenade he was holding. When Stroop's ultimatum to surrender was rejected by the defenders, his forces resorted to systematically burning houses block by block using flamethrowers and fire bottles, and blowing up basements and sewers. "We were beaten by the flames, not the Germans," survivor Marek Edelman said in 2007; he was deputy commander of the ŻOB and escaped the ghetto in its last days. In 2003, he recalled: "The sea of flames flooded houses and courtyards. ... There was no air, only black, choking smoke and heavy burning heat radiating from the red-hot walls, from the glowing stone stairs." The "bunker wars" lasted an entire month, during which German progress was slowed. While the battle continued inside the ghetto, Polish resistance groups AK and GL engaged the Germans between 19 and 23 April at six different locations outside the ghetto walls, firing at German sentries and positions. In one attack, three units of the AK under the command of Captain Józef Pszenny ("Chwacki") joined up in a failed attempt to breach the ghetto walls with explosives. Eventually, the ŻZW lost all of its commanders. On 29 April, the remaining fighters from the organization escaped the ghetto through the Muranowski tunnel and relocated to the Michalin forest. This event marked the end of significant fighting. At this point, organized defense collapsed. Surviving fighters and thousands of remaining Jewish civilians took cover in the sewer system and in the many dugout hiding places hidden among the ruins of the ghetto, referred to as "bunkers" by Germans and Jews alike. The Germans used dogs to detect such hideouts, then usually dropped smoke bombs to force people out. Sometimes they flooded these so-called bunkers or destroyed them with explosives. On occasions, shootouts occurred. A number of