It is not as if the countries lack resources. Their fast growing population does [0]. So far, Europe does not seem to be willing to repudiate the asylum treaties it signed, so the young men always have the option to try and reach Europe(an resources) under the guise of seeking protection. And once they are in, their forced removal is unlikely [1], so they cease to be a resource problem for their country of origin and start to be a resource problem for the new host society.

The military does not even play a role here. All the poorer countries need to do is a) not prevent their own young people from leaving, b) not prevent activity of smuggler gangs, c) complicate deportations by refusing to issue passports to their citizens who destroyed their papers underway. None of those actions need guns, much less superior guns.

[0] ... India and Brazil aren't really in the "top population growth" league. Look up population pyramids of Niger, Ethiopia, Nigeria, Yemen. Those graphs promise future mass migration streams. (https://www.populationpyramid.net)

[1] ... https://ec.europa.eu/eurostat/statistics-explained/index.php...

Military might is not very helpful in the modern world. The NATO coalition could not hold their ground in a country such as Afghanistan nor could all of Europe prevent that the collapse of order in Syria (a country of 20m) caused a spill of 2m migrants into Europe.

Your parent was suggesting that the developed world could not deal with a collapse of India or Brazil or several populous African countries.

I wasn't even thinking about their states trying to take resources by force.

What would happen if 20% of India decided that their society has collapsed and they should migrate at any cost to some developed country?