[18] Founded in Beirut in 1932 as a national liberation organization hostile to French colonialism, the party played a significant role in Lebanese politics and was involved in attempted coup d'etats in 1949 and 1961 following which it was thoroughly repressed.

By that time, the SSNP-L had grown exponentially and had clashed on many occasions with its primary ideological rival, the Lebanese nationalist Kataeb Party (also known as the "Phalange" or "Phalangists"), which was committed to the notion of Lebanon in its French borders.

On 4 July 1949, a year after the declaration of the establishment of the state of Israel and the 1948 Arab–Israeli War, and as a response to a series of aggressions perpetrated by the Kataeb-backed central government, the SSNP-L attempted its first revolution.

Following a violent crackdown by government forces, Saadeh traveled to Damascus to meet with Husni al-Za'im in an attempt to obtain his support, although he was handed over to Lebanese authorities, and executed on July the 8, 1949.

With the outbreak of the Cold War and the rise of Marxist and communist influences supported by the USSR, the SSNP-L found itself facing a new ideological adversary, especially that most left-wing movements in the Middle-East rallied around Gamal Abd El Nasser and Arab nationalism.

[23][24] In the scholarly literature, the coup has been explained as stemming from the party's ideological preference for violence ("bullets over ballots"), its frustration at exclusion from the Lebanese state, and both political and military criticism of the rule of Fouad Chehab.

The SSNP-L found its natural allies to be the Palestinian guerrillas, mainly Fatah and the PFLP as well as its former bitter enemies: the left-wing Arab nationalist movements, the Syrian Ba'ath Party, and the communists.

One of the best-known sparks of the resistance was the killing of two Israeli soldiers in the Wimpy Cafe on west Beirut's central Rue Hamra by party member Khalid Alwan.

[28] A party member Sana'a Mehaidli, who committed a suicide attack at the age of 16 against an Israeli checkpoint in Lebanon, is considered "the progenitor of all female martyrs for the Palestinian cause".