Across the nation, traffic stopped and Israelis stepped out of their cars on streets and highways to observe two minutes of silence when the sirens sounded at 11 a.m.
This year, Israel remembers more than 20,000 soldiers and fighters killed in battle since the start of Zionist settlement at the turn of the century.
Flowers covered the graves of soldiers at military cemeteries, flags flew half-staff, and radio and television stations broadcast mournful songs and interviews with relatives of men and women who died during compulsory military service.
"We come here to unite and remember," Prime Minister Benjamin Netanyahu said during a ceremony at Mount Herzl National cemetery in Jerusalem.
"No nation can assure its security, existence, or future if it does not have the inner preparedness to pay the heavy price in the struggle for national existence," Netanyahu said.
Thousands left roses and carnations at the cemetery's pink limestone graves, gleaming in brilliant sunshine. An elderly woman draped in a shawl stooped over a grave, sobbing.
Across town at the Cinematheque cafe, a young woman dressed in bright summer colors put down her orange juice and stood to gaze at the Old City walls - the site of fierce battles in the 1967 and 1948 wars. She wept.
The mourning was marred by scuffles in the ultra-Orthodox Jerusalem neighborhood of Mea Shearim, where signs had been posted instructing residents to make a point of conducting their business while the sirens sounded.
The ultra-Orthodox regard such displays as heathen icons and believe that mourning must come through the recitation of psalms and the study of religious texts.
When the sirens began, an angry crowd of ultra-Orthodox Jews assailed a television crew at an intersection, amid a column of drivers standing silently next to their cars. A woman was knocked to the ground by ultra-Orthodox men who tried to grab her video camera.
Other ultra-Orthodox Jews heeded a call by a prominent religious lawmaker to stand attention out of respect for secular Israelis, who constitute the bulk of military conscripts.
Places of entertainment shut down when the period of mourning started at sundown on Monday. The country's leading rock stars drew thousands to Tel Aviv's Rabin Square for a memorial concert that was marked by a respectful absence of applause.
The mood abruptly shifts at sundown Tuesday, when Israelis usher in the country's 51st Independence Day with barbecues and air shows.
Palestinians in the West Bank and Gaza Strip were barred from entering Israel during the two-day holiday.
By DINA KRAFT