  I : Chiral Perturbation Theory is introduced and its applications to
semileptonic and nonleptonic kaon decays are discussed.
  II: The method of large $N_c$ is used to calculate $K\to\pi\pi$ nonleptonic
matrix elements, in particular the matching procedure between long and
short-distance evolution that takes all scheme dependence correctly into
account is discussed. Numerical results reproduce the $\Delta I=1/2$ rule
without the introduction of any free parameters.
