Military and church careers for younger sons

What about third and fourth sons when a ruling family sends its second son to war?

The suggested pattern puts a third son into the church and a fourth into naval or colonial service, while keeping the second son available as a substitute heir.

The explanation assigns different expectations to sons according to their place in the succession. The eldest is prepared to inherit, while the second needs to remain available if the heir dies without becoming an immediate rival. Military service elsewhere in Europe offers one way to manage that tension. A third son might enter the church, while a fourth could seek a naval or colonial career. These are suggested family strategies rather than a fixed career rule for every younger son.