If you announce it, there are often counter measures to the counter measures. Once the enemy knows, the reliability begins to degrade. E.g. mirror finishes can disperse laser strikes, jinking can doge orbital rail guns, or dummy submunitions can overwhelm interceptor shields. Yes, these can be countered in turn, but you now have a new technological arms race.
There’s also the first strike problem. If you are going to be invulnerable, then a first strike might be reasonable, before the system comes online. This was actually part of the reason the “Slam” project was stopped (a viable, but utterly batshit insane weapon system). They were worried that if the USSR got wind of it, they might decide a first strike, before it came online, was the only reasonable response.
It depends on the reliability.
If you announce it, there are often counter measures to the counter measures. Once the enemy knows, the reliability begins to degrade. E.g. mirror finishes can disperse laser strikes, jinking can doge orbital rail guns, or dummy submunitions can overwhelm interceptor shields. Yes, these can be countered in turn, but you now have a new technological arms race.
There’s also the first strike problem. If you are going to be invulnerable, then a first strike might be reasonable, before the system comes online. This was actually part of the reason the “Slam” project was stopped (a viable, but utterly batshit insane weapon system). They were worried that if the USSR got wind of it, they might decide a first strike, before it came online, was the only reasonable response.