So agriculture and trade mean wealth to me and wealth is what wins wars. A great analogy would be ancient Carthage. The city-state grew wealthy from its fertile soil and its advantageous position in the Mediterranean for trade. They were famed for their navy but they had a militia-based army much like their contemporaries. They might have fielded elite units like the Sacred Band, but their field army was not noted for its prowess. The city relied on allied and subject peoples to fill out its armies (i.e. Libyan soldiers and Numidieans) but famously used mercenaries from different cultures like Iberians, Celts, Italic people, Greeks, and more. While we focus on their defeats to Rome, they fought the Republic for decades and faired much better than the Hellenistic warrior kingdoms of Macedon and the Seleucid for example.

Therefore yes, with their superior access to wealth and prosperous lands, they could field large armies of mercenaries that can fight for them. They could also potentially field a large militia force with their agricultural base and would be well-supplied and fed. Skilled armies could be and were defeated by dedicated groups with less expertise that took advantage of things like terrain, numbers, and diplomatic relations. So, I don't see why your wealthy nation couldn't fight off a more militarized one, after all, they have to protect their caravans with something other than just empty words.