(a)When defendant may bring in third party.At any time after commencement of the action a defendant, as a third-partyplaintiff, may cause a summons and complaint to be served upon a person not a partyto the action who is or may be liable to him for all or part of the plaintiff'sclaim against him. The third-party plaintiff need not obtain leave to make theservice if he files the third-party complaint not later than 14 days after heserves his original answer. Otherwise he must obtain leave on motion uponnotice to all parties to the action. The person served with the summons andthird-party complaint, hereinafter called the third-party defendant, shall makehis defenses to the third-party plaintiff's claim as provided inRule12 and his counterclaims againstthe third-party plaintiff and cross-claims against other third-party defendantsas provided inRule 13. The third-party defendant mayassert against the plaintiff any defenses which the third-party plaintiff hasto the plaintiff's claim. The third-party defendant may also assert any claimagainst the plaintiff arising out of the transaction or occurrence that is thesubject matter of the plaintiff's claim against the third-party plaintiff. Theplaintiff may assert any claim against the third-party defendant arising out ofthe transaction or occurrence that is the subject matter of the plaintiff'sclaim against the third-party plaintiff, and the third-party defendantthereupon shall assert his defenses as provided inRule12 and his counterclaims andcross-claims as provided inRule 13. A third-party defendant mayproceed under this rule against any person not a party to the action who is ormay be liable to him for all or part of the claim made in the action againstthe third-party defendant.
(b)When plaintiff may bring in third party.When a counterclaim is asserted against a plaintiff, he may cause a third partyto be brought in under circumstances which under this rule would entitle adefendant to do so.