pedaitsky:
You're new here, so just for future reference: This thread should have been posted in the Troubleshooting forum, as it deals with a gameplay related question. I have taken the liberty of moving it for you.
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As far as your question goes, the "Engage" command tells the bots to seek out the enemy. It's basically an attack command. However if you play Assault games, then the command; which is actually "Engage according to operational paramaters." orders the bots to move ahead with the mission, going through the proper checkpoints (as specified by the mission), and attack whenever the opportunity arises.
Welcome to Infiltration, and I hope you enjoy your time within our community.