增援 is a separable verb (离合词) meaning to send additional forces or resources to support someone in a difficult situation, most commonly used in military, police, or emergency contexts. When you insert a duration, measure word, or aspect marker, the verb splits: 增了援 ('sent reinforcements'), 增过一次援 ('reinforced once'). The person or unit receiving the reinforcement is introduced with preposition 给 or comes before the verb.