BEKAA VALLEY, Lebanon — Since it erupted in March 2011, the Syrian war has seen heavy involvement by Lebanese Hezbollah, which has increased its presence there since 2013 to prop up the regime of President Bashar al-Assad.

Military sources close to Hezbollah estimate that the militant group may have deployed 7,000 to 9,000 fighters in Syria, specifically in areas around Damascus. The civil conflict has caused a large number of casualties among its ranks, with around 1,300 fighters killed in the last five years, according to the news website Ya Libnan.

In May 2015, the leader of Lebanese Hezbollah, Hassan Nasrallah, said in a speech that his fighters would expand their presence in Syria. With the increasing participation of Hezbollah fighters on various fronts from the north to the south of Syria, the militant group is relying more and more on youth from the Bekaa Valley, in south Lebanon and Beirut, the military sources told Al-Monitor on condition of anonymity.

These sources underline that Hezbollah is relying on younger recruits for several reasons, the biggest being that the party does want to focus all its resources on Syria and wants to keep some of its old guard for the protection of the southern front line in Lebanon.