It’s not as serious as it seems, but it was the general thinking behind the first Intruder-flies Ed Ward, Jerry French and Scott Howell tied, sometime in the early 90ies. They discovered that big flies would illicit aggressive strikes – because the “intruded the personal space” of big fish, without spooking them. To begin with they used them for king salmon and then slowly transferred the style of fly to steelhead fishing.