This is a randomized, multicenter, open-label, two-arm study in treatment-naive participants with operable, locally advanced, or inflammatory, centrally-assessed HER2-positive early breast cancer (EBC) whose primary tumors were greater than or equal to (\>/=) 2 centimeters (cm). The study was designed to evaluate the efficacy and safety of trastuzumab emtansine + pertuzumab (experimental arm; T-DM1 + P) versus chemotherapy, trastuzumab + pertuzumab (control arm; TCH + P). The study comprised a neoadjuvant treatment period, followed by surgery, and an adjuvant treatment period. Treatment can be stopped due to disease recurrence, unacceptable toxicity, withdrawal of consent, or study termination.