But there are delayed weapons and it's also possible to use weapons that other nations use. Even if the military thinks that know who did it doesn't mean the pe

But there are delayed weapons and it's also possible to use weapons that other nations use. Even if the military thinks that know who did it doesn't mean the people will believe it, especially when there are disinformation campaigns. You can't fight a war if your own population doesn't support you/it. A hostile nation doesn't have to be able to do this completely undetected, they simply have to create enough doubt.