Question: In ancient times, why was the geographical location of the country that secured southern Lebanon in 1978 strategic?

Knowledge 1: Israel
On 11 March 1978, a PLO guerilla raid from Lebanon led to the Coastal Road Massacre. Israel responded by launching an invasion of southern Lebanon to destroy the PLO bases south of the Litani River. Most PLO fighters withdrew, but Israel was able to secure southern Lebanon until a UN force and the Lebanese army could take over. The PLO soon resumed its policy of attacks against Israel. In the next few years, the PLO infiltrated the south and kept up a sporadic shelling across the border. Israel carried out numerous retaliatory attacks by air and on the ground. [SEP] Knowledge 2: Iran
At its greatest extent, the Achaemenid Empire included the modern territories of Iran, Azerbaijan, Armenia, Georgia, Turkey, much of the Black Sea coastal regions, northeastern Greece and southern Bulgaria (Thrace), northern Greece and Macedonia (Paeonia and Ancient Macedon), Iraq, Syria, Lebanon, Jordan, Israel, Palestine, all significant ancient population centers of ancient Egypt as far west as Libya, Kuwait, northern Saudi Arabia, parts of the UAE and Oman, Pakistan, Afghanistan, and much of Central Asia, making it the first world government and the largest empire the world had yet seen.
Knowledge 1: Israel
On 11 March 1978, a PLO guerilla raid from Lebanon led to the Coastal Road Massacre. Israel responded by launching an invasion of southern Lebanon to destroy the PLO bases south of the Litani River. Most PLO fighters withdrew, but Israel was able to secure southern Lebanon until a UN force and the Lebanese army could take over. The PLO soon resumed its policy of attacks against Israel. In the next few years, the PLO infiltrated the south and kept up a sporadic shelling across the border. Israel carried out numerous retaliatory attacks by air and on the ground. [SEP] Knowledge 2: Mount Hermon
The springs, and the mountain itself, are much contested by the nations of the area for the use of the water. Mount Hermon is also called the ``snowy mountain, ''the`` gray - haired mountain'', and the ``mountain of snow ''. It is also called`` the eyes of the nation'' in Israel because its elevation makes it Israel's primary strategic early warning system.
Knowledge 1: Israel
On 11 March 1978, a PLO guerilla raid from Lebanon led to the Coastal Road Massacre. Israel responded by launching an invasion of southern Lebanon to destroy the PLO bases south of the Litani River. Most PLO fighters withdrew, but Israel was able to secure southern Lebanon until a UN force and the Lebanese army could take over. The PLO soon resumed its policy of attacks against Israel. In the next few years, the PLO infiltrated the south and kept up a sporadic shelling across the border. Israel carried out numerous retaliatory attacks by air and on the ground. [SEP] Knowledge 2: Great power
Japan and Germany are great powers too, though due to their large advanced economies (having the third and fourth largest economies respectively) rather than their strategic and hard power capabilities (i.e., the lack of permanent seats and veto power on the UN Security Council or strategic military reach). Germany has been a member together with the five permanent Security Council members in the P5+1 grouping of world powers. Like China, France, Russia and the United Kingdom; Germany and Japan have also been referred to as middle powers.

Answer: its elevation makes it Israel's primary strategic early warning system