A scenic view is given of the main sequence of developments related to the Dirac Equation since it was proposed as a single particleequation in an external field. Attention is drawn to the fact that analternative form of the Dirac equation in terms of antisymmetrictensor fields (ATF) had first been proposed by Ivanenko and Landau. and much later by Kählar. a formulation which has found considerableuse in lattice QCD theory. Next, the sequenceof developments in respect of two-particle relativistic equations are formed―from the Bethe―Salpeter Equation on the one hand,tothe two-particle Dirac Equations with constrained Hamiltonians onthe other. together with their points of similarity and contrast.Finally.A brief sketch is given of the Dirac Equation Via the ATFformulation (using the language of external differential forms)whose main features include among other things a doubling ofthe spin content and a unifying role in the formulation of SUSYtheories.

Gauge field, Chiral invariance,Dirac equation, Goldstone pion field,Gluon field