Is this a sentence fragment?

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1

<p>The following is a sentence from a reading passage:</p>

<p>Yet the Roman emperors, from fear of liberty, since the time of Augustus had systematically disarmed the citizens and trusted the defense of the Empire to mercenaries.</p>

<p>I can’t see the main verb; is this a grammatical error? :(</p>

2

<p>“Yet”, “from fear of liberty”, “since the time of Augustus” can be left out.
The sentence therefore can be rewritten as: “the Roman emperors had systematically disarmed … and trusted …”
The main verb is “had disarmed” and “had trusted”</p>