Twelve weeks to 13.1 miles, on 3 runs a week. Three days is a deliberate choice, not a compromise. A first half marathon is won by getting the long run done and arriving at the start line healthy, and for most people that is far easier on 3 quality days than on 5 rushed ones. Tuesday is an easy run, Thursday grows from a recovery run into steady work and eventually into half marathon effort, and Saturday is the long run that carries the plan. A strength session and one optional cross-training ...