Lebanese soldiers have deployed along the border with Israel, after almost all the remaining Israeli soldiers withdrew on Sunday.
The Lebanese soldiers have been warmly welcomed
The deployment comes six weeks after the UN-brokered ceasefire that ended fighting between Israel and Hezbollah.
The soldiers are taking up positions in south Lebanon the army has not held in four decades.
Israel sent thousands of troops into southern Lebanon after Hezbollah abducted two of its soldiers in July.
Women in the village of Marwaheen welcomed the Lebanese soldiers by throwing rice and rose petals at them as they arrived.
Marwaheen was heavily damaged in the fighting.
In a small ceremony near the border, Lebanese army commander Brig Gen Michel Suleiman promised to reassert Beirut's control of the area by stopping arms smuggling and cross-border attacks from either side.
He urged his soldiers to take tough action against Israel too, if needed. "I call on you to confront any Israeli aggression and violations," he said.
Since the late 1960s, south Lebanon has been controlled by various armed groups, including Hezbollah.
The UN ceasefire resolution called on Hezbollah to end attacks against Israel and on Israelis to withdraw.
Resolution 1701 called for the deployment of 15,000 UN peacekeepers, alongside the same number of Lebanese troops, in south Lebanon.
Some 5,000 UN forces are now in place, together with the 15,000 Lebanese soldiers.
Israel has withdrawn the bulk of its troops from Lebanon, fulfilling a key condition of the UN ceasefire that ended its war with Hezbollah.
But a few Israeli troops remain in the Lebanese side of the divided village of Ghajar.
Lebanese troops have not been in south Lebanon for decades
The UN said it expects the Israeli army to leave Ghajar this week.
The resolution also calls for the disarming of Hezbollah - which the militant group has resisted.
Hezbollah is still holding two Israeli soldiers whose abduction sparked off the conflict.
The UN has appointed a mediator to try to win the captured soldiers' freedom, most likely through a prisoner swap with Israel.
More than 1,100 people - mostly civilians - were killed in Lebanon during the war. More than 150 Israelis - mainly soldiers - were killed.