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We present O, Na, and Fe abundances, as well as radial velocities, for 113red giant branch (RGB) and asymptotic giant branch (AGB) stars in the globularcluster M13. The abundances and velocities are based on spectra obtained withthe WIYN-Hydra spectrograph, and the observations range in luminosity from thehorizontal branch (HB) to RGB-tip. The results are examined in the context ofrecent globular cluster formation scenarios. We find that M13 exhibits many keycharacteristics that suggest its formation and chemical enrichment arewell-described by current models. Some of these observations include: thecentral concentration of O-poor stars, the notable decrease in [O/Fe] (butsmall increase in [Na/Fe]) with increasing luminosity that affects primarilythe "extreme" population, the small fraction of stars with halo-likecomposition, and the paucity of O-poor AGB stars. In agreement with recentwork, we conclude that the most O-poor M13 giants are likely He-enriched andthat most (all?) O-poor RGB stars evolve to become extreme HB and AGB-manqu\'estars. In contrast, the "primordial" and "intermediate" population stars appearto experience standard HB and AGB evolution.

Oxygen and Sodium Abundances in M13 (NGC 6205) Giants: Linking Globular Cluster Formation Scenarios, Deep Mixing, and Post-RGB Evolution