President Shimon Peres leaves for Poland today on a four-day state visit that will focus on the 65th anniversary of the Warsaw Ghetto uprising. While in Warsaw, he is scheduled to visit with Irena Sendler, a former nurse and social welfare department employee, who during World War II helped save the lives of some 2,500 Jewish children. The daughter of a doctor whose patients were mainly poor Jews, Sendler witnessed even greater deprivation in Warsaw's large Jewish community following the Nazi invasion of Poland. After the establishment of the Warsaw Ghetto, Sendler received a special permit that allowed her access to the ghetto at all times so that she could help combat contagious diseases. This enabled her to provide starving Jews with food, money and clothing. But the true purpose of her frequent visits was to smuggle as many Jewish children as possible out of the ghetto and place them with non-Jewish families. She recruited other social workers to provide false identities for these children. Sendler devised a code with the children's real names and other details, and stored the information in glass jars, which she then buried in her garden. In 1965, Yad Vashem named her Righteous among the Nations, and in 1991, she was made an honorary citizen of Israel. Other Righteous among the Nations are expected to attend Tuesday's ceremony honoring the Warsaw Ghetto fighters. The event is scheduled to take place in a square dominated by the famous monument by Warsaw-born sculptor Natan Rapoport, a replica of which stands in Yad Vashem's Warsaw Ghetto Plaza. Also attending will be Holocaust survivors and IDF officers. Peres and Polish President Lech Kaczynski will address the gathering. Kaczynski has frequently denounced anti-Semitism and is quite familiar with Jewish heroism in Poland. Among the Holocaust survivors accompanying Peres to Poland are three who were among the fighters in the Warsaw Ghetto - Simcha Rotem, Pnina Greenspan and Luba Gevissar - all in their eighties. Rotem is the most famous, having fought not only in the Warsaw Ghetto Uprising in April, 1943, but also in the Polish Warsaw Uprising in August 1944. His Aryan looks and his accentless Polish made the teenage Rotem, then known as Szymon Ratheiser, a natural courier. When it became obvious that the uprising was a lost cause, he was sent to the Aryan side to meet with Yitzhak Zuckerman, who was deputy to Mordechai Anielewicz. Together they tried to work out an escape route for the remaining fighters. But the Nazis discovered the route and Zuckerman and Rotem remained trapped on the Aryan side. But Rotem was determined to go back into the ghetto, and after several futile attempts finally succeeded in working his way through the sewers. He found Zivia Lubetkin, one of the leaders of the uprising and a group of approximately 80 fighters. He retraced his steps and led them out of the ghetto, via the sewers and into the forests beyond the city. After the war he was engaged in Aliya Bet operations that entailed smuggling Jewish refugees past the British authorities into pre-state Palestine. He was also a member of the Avengers, an execution squad made up of members of wartime Jewish resistance organizations who doggedly tracked down Nazi war criminals and meted out their own kind of justice. Peres is scheduled to hold other meetings with Kaczynski, as well as with Polish Prime Minister Donald Tusk, whom he met last week during the latter's official visit to Israel. Before the ceremony, Peres will visit the Umschlagplatz, where the Nazis assembled Jews and others designated for death for transportation to Treblinka. Following the memorial ceremony, Peres is scheduled to meet with 160 Holocaust survivors, both from the Warsaw Ghetto and from the Sobibor death camp. Some quarter of a million people, mostly Jews, were murdered in Sobibor, the second death camp to begin operating. John Demjanjuk, who was extradited from the United States in 1986 to stand trial in Israel for war crimes, was identified by Holocaust survivors as a notoriously cruel guard at both Treblinka and Sobibor. On Wednesday, Peres is due to address 1,000 students at Warsaw University, and on Thursday, prior to returning to Israel for Pessah, he is scheduled to address the Polish Parliament.