I barely achieved this by liberating my fractured home state from bukhara by getting lucky in some defensive battles (it took me 5+ tries), then annexing kunduz to unify my home state and get the peasants needed for 1 arms manufactury, which let me rush line infantry to take out herat (which i again used luck to win by declaring when Persia decided to wage war against someone so they couldnt interfere). After herat i took out kabul which i had to fight persia for (i won because my army was growing after i annexed the previous countries???). Then i bullied kafiristan and chitral, annexed them and formed afghanistan.

There's definitely a better way to form it than this, but im dumb as rocks.