Under what circumstances may the noun 'ambush' not be preceded by any article?

In particular, I wish to know if they were attacked from ambush and they were attacked from an ambush are equally in fashion. The articled form is is definitely more familiar, but look at the first definition in https://www.merriam-webster.com/dictionary/waylay .

Might one say that the unarticled usage is passé ? Please cite current usage examples if you can.