It also surprised U.S. commanders because in recent months Iranian forces have conducted exercises and operations in the region in a professional manner
If that is accurate and not just CNN trash-talking, then it would indicate that those "U.S. commanders" do not understand the nature of the Muslim enemy that they are facing, which is indeed a dangerous state of affairs.
Iran can not be trusted to behave in a way that normal human beings are expected to behave, because at heart they are savages driven by a totalitarian ideology that is beyond the comprehension of typical civilized people.
After all this time, you would expect "U.S. commanders" to know better, even if the idiots in Obama's and Kerry's State Department remain clueless.
The Iranians are playing Obama/Jarrett similar to the way Hitler played Chamberlain. Israel and the Arabs know this. Thus the offensive into Yemen. US military needs to expect an all out move by the Iranians real soon now. Why ? They know Obama is the weakest President they have ever seen. They also know their allies in Yemen need a diversion. We will shortly see Obama pounding the podium while pointing his finger at us proclaiming, I did not have sex with that Iranian.