The Enterprise Incident gave us the theory or idea that Klingons and Romulans were allies against the Federation. But the other theory is that that stole Klingon technology. The real reason was that the producers were so happy with the Klingon spaceship design that they decided to implement it in every conceivable chance they got plus also they had lost the Bird of Prey model from Balance of Terror for further usage!
I like to think that the Klingons and Romulans had started an alliance and began to trade technology with the Klingons acquiring cloaking devices while the Romulans got state of the art ships in their defiance of the Federation pushing them back beyond their borders!
JB
I like to think that the Klingons and Romulans had started an alliance and began to trade technology with the Klingons acquiring cloaking devices while the Romulans got state of the art ships in their defiance of the Federation pushing them back beyond their borders!

JB