Simple enough. If any or all of these three ships simply disappear, particularly if coincidental with the beginning of widescale US military operations in Iraq, that will serve as a message to those aboard other vessels with similar missions that the same fate can also befall them.
If that causes them to abandon their planned missions, swell. If it just makes them jumpy enough that they deviate from their preplanned routines and thereby identify themselves as having a possibly hostile intent, that will suffice.
Accordingly, the fate of those first three ships deserves to be publicised. We may hear far less about other later *shipping accidents.*
-archy-/-