If pre-Second exile jews like Avraham, Moshe, David, Shimshon, Yiftach, Gidon, Chizkiya, Yoshiya, the Maccabees etc, saw today all of Jerusalem in Jewish hands, davka except the Har Habayis, they would immediately take it, regardless, or rather specifically because of its worldwide consequences!
The reason no one does it today is because the length and depth of the Second Exile has so penetrated our bones, that no one today has the courage...and worse...everyone is quite happy with the status quo.
Which is why the Zohar says that it is not the goyim who start up with the Moshiach, but it is the Moshiach who will first declare war on the goyim, of which his taking of the Har Habayis will be just the first act!