Braised Sausage with Olives and Potatoes

In a heavy kettle heat the oil over moderately high heat until it is hot but not smoking, in it brown the sausage in batches, transferring it as it is browned to paper towels to drain, and pour off all but 1 tablespoon of the fat. In the fat remaining in the kettle cook the onion and the garlic over moderate heat, stirring, until the onion is golden, stir in the tomatoes with the juice, breaking up the tomatoes, and the sausage, and simmer the mixture, covered, for 30 minutes. Stir in the potatoes, peeled and cut into 3/4-inch pieces, and the olives, simmer the mixture, covered partially, for 15 to 20 minutes, or until the potatoes are tender, and season it with salt and pepper.