Atomically precise on-surface synthesis of graphene nanoribbons (GNR) with well-defined width and edge configuration has been widely advanced during the last decade. The main bottom-up growth strategy relies on the thermally activated Ullmann-like coupling reaction followed by the cyclodehydrogenation of tailor-made precursors to achieve the desired precision. We present a systematic investigation of the growth mechanism of chevron GNR on the Ag(111), Au(111) and Cu(111) surfaces in ultrahigh vacuum (UHV). We found that the multistep reaction follows different pathways with different activation temperatures depending on the supporting surface. The importance of the as-released Br and their potential influence on the growth process are discussed. The different intermediate states were investigated by low-temperature Scanning Tunneling Microscopy in combination with Thermal Desorption Spectroscopy and Kinetic Monte Carlo simulations.