The announcement is done to achieve two things: 1. Posture to their own populace that they're not backing down (thus winning political scores) 2. Show to the

The announcement is done to achieve two things: 1. Posture to their own populace that they're not backing down (thus winning political scores) 2. Show to the rest of the world that they are leadership to reckon with, that they don't back down cowardly. Imagine two high-school teens with some social status fighting on the playground. They will not back off because of social status reasons. Only here, the teens have nukes.