VIDEO - Tens of thousands of Hamas supporters marked the Islamic group's 21st anniversary with an outdoor rally Sunday, and the show of strength included a play featuring a mock-captive Israeli soldier begging for his freedom. Hamas was founded in Gaza in December 1987, and seized control of the territory by force in June 2007. Sunday's rally was further evidence of Hamas' unchallenged control over 1.4 million people, with thousands of Hamas policemen securing Gaza City streets. The huge crowd filled an outdoor area that can hold at least 150,000 people, and nearby streets were also thronged with Hamas supporters. Many wore baseball caps and waved flags in Hamas' signature green color. During a colorful ceremony that included songs and plays, Hamas loyalists paraded a mock-captive Israeli soldier, who in Hebrew begged to return home. "I miss my Mom and Dad," said a Hamas loyalist, dressed in an Israeli soldier's uniform, in a clear reference to captured Israeli soldier Gilad Shalit, seized by Hamas-backed Palestinian terrorists in June 2006. Mock-Gilad Shalit play (Video courtesy of Infolive.tv) Egyptian-mediated negotiations to exchange Shalit for hundreds of Palestinian prisoners have repeatedly foundered. "For those who made my children swallow a bitter drink, you will drink from the same cup," intoned a voiceover. Senior Hamas leaders are to speak at the rally, laying out the future of an Egyptian-mediated truce with Israel and the group's relations with rival Palestinian movement Fatah, which rules the West Bank.