article_snippet.sent: For one thing, it has a lot more people -- about a million, one Obama administration official noted.
article_snippet.sent: Calling for "patience," an administration official said that winning Mosul is a complex endeavor.
article_snippet.sent: a complex endeavor will "take a lot of capacity," an administration official said, "and some time to build.
highlights_snippet.sent: Officials note that recapturing Mosul from ISIS could be a complicated endeavor .