The Syrian conflict has stretched on for eight years, pulling in players as disparate as Russia, Iran, Turkey, Israel, and the US, as well as creating the ideal conditions for the rise of ISIS.
It's also become another testing ground for tactics and technology.
As Russia, backing the Assad regime, asserts more power in Syria, it's also become a proving ground for new Russian technologies.
"Syria is not a shooting range for Russian weapons, but we are still using them there, our new weapons," Russian President Vladimir Putin said in a public address last year.
"When we started to use these modern weapons, including missiles, whole teams from our defense industry companies went to Syria, and worked there on-site — it is extremely important for us — to finalize them and figure out what we can count on when using them in combat conditions."
Russian state media outlet TASS reported in 2018 that Russia had tested 210 weapons in Syria. In December of that year. Russian Deputy Prime Minister Yury Borisov told Russian media that the Russian military had begun using the Tupolev Tu-160 supersonic stretegic bombers, the Iskander-M ballistic missile system, and the Pantsir S1 anti-aircraft missile in Syria.
But innovation has gone the other way, too — the Russian military has started developing small drones equipped with ordnance after seeing ISIS deploy them in Syria.
And in the conflict that's morphed from a popular uprising against a dictatorial dynasty, swelling in the intoxicating first flush of the Arab Spring, to become synonymous with desperation, despair, displacement, and brutality. Bashar al-Assad, whose regime is consistently plumbing the depths of inhumanity, is still in power; and astoundingly, due to the latest failure in American policy, stands to regain control of much of what his regime lost, first to rebels, then to ISIS, then to Kurdish-led forces backed by US troops.