This most embarrassing "lassen" again.
I've been meditating on this sentence since early in the morning but still can figure out neither the role of "lassen" here, nor the grammar construction used, and thus, cannot get its exact meaning. Every time I come across "lassen", I'm in panic. No visible progress over time.
I've come across this sentence in today's DW news: "Erdogan hat angekündigt, seine Truppen im Nordwesten Syriens weiter in Richtung Idlib vorrücken zu lassen."
I'm also interested in the native or experienced speakers' comments here.
My (a humble fellow learner's) speculations go like this:
To move the troops forward - Truppen vorrücken lassen (Leo)
So it's something like let meaning unleash here. I've also seen this: um keine Zweifel aufkommen zu lassen - to exclude any doubt, which is equal to not to let any doubt occur.
So, in this particular piece of news I guess it as "Erdogan has announced that he will let his troops to move on in the North-West of Syria to advance towards Idlib." Or something like that.
I doubt the translation with unleash here. I think lassen simply implies that it is not a direct action. Eg. er kocht (he cooks) vs. er lässt kochen (he get's somebody else to cook). In the example above he orders the troops to move forward (maybe he tells a general to tell the troops to do it, he is not necessarily with them). But if the sentence would be Er rückt mit seinen Truppen vor it would be certain that he is with them.
Your speculations are mostly on point.
I disagree only with one small thing of your example "to exclude any doubt, which is equal to not to let any doubt occur.". I dont think these are equal and instead I think theyre only similar. The excluding is the stronger action of those two.