The act-as-one provision compels the reinsurers to act in concert in the selection of the arbitration panel and in all major communications and decisions concerning the dispute. It reserves to the reinsurers the right to assert their own claims or defenses, and it is does not impair the several liability that typically exists under most reinsurance agreements. It allows the arbitration process to move forward without confusion as to how many arbitrators the disputing parties will appoint. Essentially, it treats the reinsured as one party (which it is) and the reinsurers' as one party when the dispute involves more than one reinsurer. This way, the two "parties" or sides can each appoint one arbitrator, and the party-appointed arbitrators can appoint the umpire, fulfilling the contractual requirement of a three-arbitrator panel.