From The Jerusalem Post:
The chief rabbis of Israel called this week on secular Jews to join their religious brethren in fasting on Tisha Be'av as a way of showing solidarity and unity at a time of war. "Those brothers and sisters who usually do not fast should make a special effort to do so this year to express the pain of those adversely affected by the war," wrote Ashkenazi Chief Rabbi Yona Metzger and Sephardi Chief Rabbi Shlomo Amar.
The fast begins at sundown on Wednesday night and ends on Thursday at about 8 p.m.
"The Israeli nation is connected one to the other by mutual responsibility, the rabbis wrote. "On this day, a national day of mourning, it is especially important to show and express our pain and hurt over the dissension that caused the destruction of the Temple."