This report contains short proofs of two known matroid decomposition results, both of which are based on a decomposition algorithm of Truemper. The main result is a recent theorem of Truemper and Tseng for the class of matroids with the max-flow min-cut property, a class characterized by Seymour. The theorem says essentially that every matroid in this class is either isomorphic to F tau or is decomposable into a 3-sum in a well-defined way. The second result describes the structure of regular matroids, and is an important ingredient in Seymour's decomposition theorem for this class.