Yes, and so was the Hagana, only called Hagana for short. Upon the 1948 declaration, Lehi and Etzel merged with the Hagana into Tzahal, so as to eliminate all the internecine squabbling, and win the imminent war. It didn’t work, according to Begin’s Revolt!. The Hagana faction of Tzahal in many instances stiffed the Etzel and Lehi-nicks on the battlefield in terms of manpower and supplies, and actually destroyed munitions being brought in on the Altelena, mistakenly believing the Irgun was attempting a hostile takeover. Had the munitions on the Altelena not been destroyed, we could have kept the Jewish Quarter of the Old City of Jerusalem, and much more.
Like him or not, Ben Gurion had the foresight to bridge the very Left wing (MAPAI party-Haganah) to the very Right wing (Herut Revisionist party -Irgun-ETZEL-STERN) in order to forge a united, new nation - Israel.
There were seeds of civil war but Jewish leaders knew this was their make or break moment, something they waited for for 2,000 years and they had to (by force) put down any sedition to their authority in order to face the coming Arab onslaught.
The Irgun and Stern were absorbed into the Haganah in order to form the nascent Israel Defense Forces (Tzhahal). It worked.
The UN has been sorry the Jews survived ever since and have done everything in their power to weaken Israel.