The national anthem of Syria was adopted in 1936; the composers of the music also composed many other Arab folk songs of the Middle East region. During the time that Syria was a member of the United Arab Republic (1958-1961), the UAR anthem was in use, which consisted of the then-Egyptian anthem followed by “Ħumāt ad-Diyār”. Once Syria left the union, the anthem was again performed on its own.
During the Syrian Civil War that started in 2011, both sides of the conflict (the pro- and anti-government forces), despite using different national flags and emblems, each use “Ħumāt ad-Diyār” as the national anthem. This is possibly due to the fact that the anthem, unlike the flag, predates the current government. (The Kurdish elements in the civil war presumably use the Kurdish anthem, and the self-proclaimed Islamic State, another faction in the civil war, also have their own anthem.)
Special thanks to: Michael Bristow for the English translation of the second verse.