Was is the main verb.
Terminology varies, but was could be considered a helping verb if the sentence used the passive voice. For example:
Tom was taken to the hospital.
Someone took him there.
Your sentence is not passive; nobody "actived" the subject. It might also be considered a helping verb if it is used in the formation of the verb:
Tom was strumming on his old banjo.
That is, past continuous: BE + v-ing.
Hope this helps.
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