God has approved the Muslims to do Conquest not for worldly gain but to make the area that is not submit to the Authority of God become submissive to His Authority. Imagine if the conquest of Europe and US is successful, there will be much much less drug industry, obscene movies/music industry, less white supremacist, and most importantly the world economic system will not be backed by riba anymore, and certainly other wisdoms as well. So what is the practical steps to do the Conquest in this era (preparations, rules, etc)?
Conquest can be done but first we need an Islamic State (Khilafah). It is that simple. And we need to understand what conquest really means... The concept of Conquest in Islam is quite different from Western one... The West view conquest as overbearing dominance, whereas Islam sees it as removing the physical obstacles preventing the spread of Islam to other lands. Hence, we see that British and American dominance did not bring good to the world, but Islam's did.