The Milky Way assembly as traced by its stars and globular clusters

Over the past decade, the Gaia mission has transformed our knowledge of the Galaxy, revealing a complex assembly history shaped by multiple accretion of smaller galaxies whose remnants are now detectable as phase-space substructures in the Halo. While precise 6D kinematics are essential to trace these relics, interpretations based only on dynamics are often prone to degeneracies. The study of the chemistry of these stellar substructures opens an independent avenue to understand their nature, complementing and deepening the picture provided by dynamics alone. However, since progenitor galaxies of Halo substructures experienced similar chemical evolutionary histories and were accreted relatively early in cosmic time, the resulting differences between chemical patterns of their stellar remnants are intrinsically subtle. Capturing these faint chemical signatures requires the highest possible level of precision and homogeneity, as even small systematic offsets between different analyses can easily erase the very contrasts that chemical tagging relies on. This Thesis adopts such a homogeneous approach, using high-resolution spectroscopy to derive precise chemical abundances for field stars and globular clusters, both long recognized as fundamental tracers of Galactic evolution. Specifically, I built and analysed the largest homogeneous catalogue to date of high-resolution abundances for retrograde Halo stars, allowing for a systematic comparison between the chemistry of all different retrograde accreted substructures for the very first time. Building up on results obtained for field stars, I extended this homogeneous chemical approach to globular clusters, demonstrating that their different origin is imprinted in their chemical compositions. On top of this, I further combined dynamics and homogeneous chemistry with precise ages to tackle the most complex cases, as I show by addressing the open question on the origin of NGC 288.