The Israeli military has captured the strategic site of Beaufort Castle in southern Lebanon, in what Prime Minister Benjamin Netanyahu described as a "decisive shift" in its offensive against Hezbollah.
It comes as ground troops move ever deeper into Lebanese territory beyond their original demarcation line of the Litani River.
Meanwhile, the Israel Defense Forces (IDF) increased the zone in southern Lebanon that it has warned residents to evacuate from.
Lebanon's prime minister has accused Israel of carrying out "collective punishment".
Perched over the Litani valley, Beaufort Castle has been key to controlling the region around it since the Crusaders built it some 900 years ago. The Israeli army captured it 44 years ago in what's known in Israel as the First Lebanon War.
In a statement on Sunday following its capture, Netanyahu said it was "a decisive stage and decisive shift in our policy".
"We have broken the barrier of fear. We are taking the initiative, we are operating on all fronts - in Syria, in Gaza, in Lebanon," he said.
Netanyahu added that his aim was to "deepen and expand our grip on the places that were under Hezbollah's control".
Defence Minister Israel Katz recalled the battle 44 years ago against the Palestine Liberation Organisation (PLO) - one of the first of the Lebanon war. He said the Golani Brigade, which took it then, had returned and raised the Israeli flag above it.
So, it's a highly symbolic as well as strategic victory, as far as Israel is concerned.
In 1982 Israeli forces occupied the castle - which is just 14.5km (nine miles) from the Israeli border - but left in 2000 when they withdrew from their self-declared buffer zone in southern Lebanon.
For the Lebanese, it's the latest historic landmark to be seized in recent days, while the city of Nabatieh further north appears to increasingly be a target for the IDF.
Katz said control of the castle and the ridge it stands upon was an important step in protecting Israeli communities on the other side of the border.
The latest evacuation warning is the second time in recent days that Israel has told residents to leave the entire south of Lebanon below the Zahrani river.
"Anyone present near Hezbollah elements, facilities or means of combat endangers their life," an IDF spokesman said.
The spokesman said a "significant number of IDF ground soldiers" were involved in the operation, which was "currently expanding to additional areas".