Rule 13, Fed. R. Civ. P. distinguishes between 'compulsory' and 'permissive' counterclaims. If the defendants' claim arises out of the transaction or occurrence that is the subject matter of the opposing party's claim, then, if certain other requisites not here pertinent, are met, it is compulsory. By definition, compulsory claims are 'ancillary to the claim asserted in the complaint and [sic] no independent basis of federal jurisdiction is required.' United States v. Heyward-Robinson Co., supra at 1081. Alternatively, if the counterclaim is unconnected with the transaction out of which the primary claim arose, it is permissive, and independent jurisdictional grounds are required. Lesnik v. Public Industrials Corp., 144 F.2d 968 (2d Cir. 1944).
The threshold question to be decided is whether defendants' counterclaims arise out of the same transaction or occurrence that is the subject matter of the plaintiff's claim. If so, then the counterclaims are compulsory, and are properly before the Court. Thus, the definition of 'transaction or occurrence' is critical to this determination.
There is a substantial body of law which liberally defines the test of compulsoriness as requiring that there be not so much 'an absolute identity of factual backgrounds ...