In addition, Gantz promised Lapid he would not join a Netanyahu-led government if the prime minister faces a hearing before indictment.
Former IDF chief Gabi Ashkenazi will join them, making him the third former IDF chief in the party, in addition to Gantz and to former defense minister Moshe Ya'alon.
"Realizing the importance of this national mission, Lt. Gen. (res.) Gabi Ashkenazi has decided to join the new list," the new coalition said in a statement.
Before Gantz and Lapid officially sealed the deal, Ashkenazi tried to convince Moshe Kahlon's Kulanu to join the Blue and White list, but his efforts were rejected by Kahlon.
According to Ashkenazi's associates, he was involved in the negotiations between Lapid and Gantz over a substantial period of time.
"Over the past month, Ashkenazi intensively worked to make this union happen, making it a condition to his joining the Blue and White list," one associate said.
After burning the midnight oil to reach an understanding, Gantz and Lapid signed a rotation agreement early Thursday, announcing they will run together in the April 9 vote.
The Blue and White top 10 list of candidates for the 21st Knesset will include Benny Gantz in first place, followed by Yair Lapid, Moshe Ya'alon, Gabi Ashkenazi, Avi Nissenkorn, Meir Cohen, Miki Haimovich, Ofer Shelah, Yoaz Hendel and Orna Barbivai.
The Israel Resilience Party, in a statement, said Gantz, Lapid and Ya'alon, "decided to establish a joint list that will comprise the new Israeli ruling party."
"The new ruling party will bring forth a cadre of defense and social leaders to ensure Israel's security, reconnect to its people and heal the divides within Israeli society," the statement from Israel Resilience said.
In the joint party's Knesset list, Gantz will be placed first, Lapid second, Ya'alon third and Ashkenazi fourth. Under the agreement, the joint party will include an equal number of candidates from Israel Resilience and from Yesh Atid, and will also include candidates from Ya'alon's Telem Party.
Against the backdrop of the center's merger, the New Right Chairman Naftali Bennett called on Prime Minister Benjamin Netanyahu to form a wide right-wing bloc.
"In light of the union in the left, I urge Prime Minister Netanyahu to make an act of leadership and call on Moshe Feiglin's Zehut, Moshe Kahlon's Kulanu and Avigdor Liberman's Yisrael Beytenu—three parties that currently fail to pass the electoral threshold—to merge into one bloc, ensuring not a single Knesset seat goes to waste," Bennett said.
"The New Right is precluded from joining forces with other right-wing parties because we already submitted our Knesset list on Wednesday," he said.