Answer:
Weaknesses
Fundamentally, it comes down to their resistance to change. They denied the forces of change in their military, economy, and overall way of life. Only full citizens could be in the army. Yet, a citizen had to have the means pay a certain amount to maintain that status. If he couldn't, then he was kicked out. Take into account that over time land started becoming concentrated into the hands of a few wealthy elite. This led to massive shrinkage in the true citizen population over the decades. Around 244BC there were fewer than 700 citizens.
Even militarily, they started to lag behind. One notable example was the Battle of Leuctra where the Theban commander Epaminondas used a simple (though revolutionary at the time) echelon formation to utterly smash the Spartan army including killing their King in the fighting. This was the first time a Spartan army had been defeated by an enemy of equal strength. Epaminondas pulled the exact same trick several years later and once again beat the Spartan army who were still relying on their old tactics. This massive depletion of Spartan manhood was never really recovered in subsequent years.
Couple these defeats with the increasing fear of helot revolts due to the growth of the helot population and decline of the true citizens. This fear severely limited their foreign policy. There were plenty of lands to conquer in the aftermath of the 2nd Persian Invasion, but they Spartans had to keep a wary eye on the entire nation of peoples they enslaved and relied on to perform most non-soldierly tasks.
Step-by-step explanation:
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