Does opening a new company in a field partially similar to the previous company—after signing a pledge under duress not to work in the same field for 3 years—constitute a breach of that pledge?

Your work in a field you previously pledged not to work in is considered a violation of your previous commitment. Fulfilling a pledge is recommended by the majority of scholars, and some have even gone so far as to say it is obligatory. Contracts made under duress and pressure are not considered valid due to the absence of consent.