  This short exposition starts with a brief discussion of situation before the
completion of special relativity (Le Verrier's discovery of the Mercury
perihelion advance anomaly, Michelson-Morley experiment, E\"otv\"os experiment,
Newcomb's improved observation of Mercury perihelion advance, the proposals of
various new gravity theories and the development of tensor analysis and
differential geometry) and accounts for the main conceptual developments
leading to the completion of the general relativity: gravity has finite
velocity of propagation; energy also gravitates; Einstein proposed his
equivalence principle and deduced the gravitational redshift; Minkowski
formulated the special relativity in 4-dimantional spacetime and derived the
4-dimensional electromagnetic stress-energy tensor; Einstein derived the
gravitational deflection from his equivalence principle; Laue extended the
Minkowski's method of constructing electromagnetic stress-energy tensor to
stressed bodies, dust and relativistic fluids; Abraham, Einstein, and
Nordstr\"om proposed their versions of scalar theories of gravity in 1911-13;
Einstein and Grossmann first used metric as the basic gravitational entity and
proposed a "tensor" theory of gravity (the "Entwurf" theory, 1913); Einstein
proposed a theory of gravity with Ricci tensor proportional to stress-energy
tensor (1915); Einstein, based on 1913 Besso-Einstein collaboration, correctly
derived the relativistic perihelion advance formula of his new theory which
agreed with observation (1915); Hilbert discovered the Lagrangian for
electromagnetic stress-energy tensor and the Lagrangian for the gravitational
field (1915), and stated the Hilbert variational principle; Einstein equation
of general relativity was proposed (1915); Einstein published his foundation
paper (1916).
