I saw an interesting article on Medium.
Nassim Taleb, a very well-regarded thinker on risk, recommended this. COL (R) Pat Lang, a well-regarded guy in Army Intel and at DIA (especially WRT the Middle East), is saying similar things.
On the other hand, National Security Adviser ("NSA") McMaster may be the most capable Army officer of his generation. He's the guy who won the 73Easting Fight in 1991 and, as the Commander of 3d ACR, he made Tal Afar work (when little else was working in Iraq, outside of work the Marines were doing that soon laid the groundwork for the Anbar Awakening). One of my VMI Classmates went to Armor Officer Basic ("AOB") with him and thought McMaster was a great guy and a great officer.
OK, reading the above in such a way as to include a range of outlooks:
1) Some smart people (apparently such as LTG/NSA McMaster) favor a greater role for the US in Syria.
2) Some smart people, COL (R) Lang, think this could be a significant error.
3) None of those smart people (to include he-who-I-have-not-named, GEN [R] Petraeus) were overly anxious to go into Iraq in '03. McMaster and Petraeus served there with great success, but paid a personal price through many tours there. (Seen, for example, in Petrauus's issues in 2012.)
4) By open source accounts, we have Special Operations Forces ("SOF") types in Syria now, working on the Raqqa problem.
5) We know Iraq (the terrain, the culture, the politics and the military ramifications) better than we know Syria.
6) The Russians know Syria in a way we don't: Syria was a long time Russian/Soviet Client.
7) If we can trust the Russians, it would make a lot more sense to let Russia handle IS in Syria.
8) The possible Sarin strike indicates we may NOT be able to trust them.
9) Lang, who has a background with Chemical Weapons, is not sure Sarin was used.
10) He believes that chlorine and organic phosphate were the agents involved, which have been used by BOTH sides.
11) Assad gains nothing by using a Nerve Agent: the war has turned in his favor and use of chemical weapons is, at least, a potential "Red Line."
12) However, as Taleb has stated, it may be that Assad no longer has complete control of his military and someone was "freelancing."
Here is my opinion, which is very tentative:
---It would be a bad idea to get into a war with Putin's Russia over this, the very embodiment of Bismarck's "some damn fool thing in the Balkans, not worth the bones of a single, healthy Pomeranian Grenadier."
---Ideally, we should be able to use this strike to get Putin to be more compliant and to start seeing a need for a stable way forward that does NOT include Assad himself.
---I'm not sure there is anyone in the Trump Administration that can pull that off, not least Trump himself, EXCEPT McMaster.
---I do not like the optics of Trump feeling he needs to take a truculent approach in Syria, due to accusations of collusion with the Russians on the 2016 Election.
---I see Putin's Russia as a "Jominian" power, in the sense that it has been conferred a great advantage by the PRC's "One Belt/One Road" policy; Russia occupies the key terrain that knits together Mackinder's "Heartland." Putin is like a guy who owns a plot of land where the railroad has to go through. (To a degree, he literally is)
--I think Putin and the PRC have decided that the key to stopping Salafist-Sunni Extremism is to tilt towards Shia Iran.
---To get crossways with Putin is to get crossways with the PRC, our main (but deleveraging) creditor.
---This is one to be careful of---but we do not, however, seem to have many careful people involved, with the exception of McMaster.