Put the garlic and chilies in a skillet with the oil. Saute over medium heat until the garlic begins to change color (do not burn). Add the tomatoes, capers, and olives and cook for 5 minutes.
Stir the achovy fillets into the sauce. Season with salt and pepper and simmer over medium heat for 15-20 minutes or until the oil and tomato begin to seperate.
Cook the spaghetti in a large pot of slated, boiling water until al dente. (When serving a very large crowd we pre-boiled the spaghetti for 6 minutes, tossed with some oil and cooled in batches quickly on large metal trays. We reheated the spaghetti for approx 10 - 30 seconds in boiling water.) Drain and transfer to a heated serving dish. Pour the sauce over the top and toss vigorously. Serve hot.Serves 4.