There are tradeoffs, and in many situations machines have a clear advantage over biological organisms.

In aviation and space, there are serious issues in keeping biological organisms alive due to oxygen levels, pressure changes, and G forces. A purely autonomous system would be able to be more maneuverable in more environments than any system that also needs to keep a meat bag alive.

The other thing machines are great at is patience. Land mines can remain operational for decades, just waiting for their opportunity to detonate. Biological organisms have much higher passive maintenance costs.

I think you are both way off, we can't get a robot to flip a burger[0] it's going to be a long time for a robot to replace a special forces solider. They aren't just dumb manpower, we are talking a strategist, weapons specialist, paratrooper, negotiator plus a dozen other roles all in a 6 foot tall, 200 pound package that can go into a country and forage off the land for months while waiting for the perfect opportunity to complete it's mission.

[0] I know you can find something on Youtube but if it really worked at scale McDonalds would be rolling them out yesterday.

People said the same thing on the advent of the Air Force. It turns out there's a lot more involved in winning a war than murdering people.