Greenwell, along with his English wife Doris (née Rubinstien), fled the Spanish Civil War. After briefly coaching in Turkey, he went to in Peru in 1939, as manager of both Universitario de Deportes and the Peruvian national team. He coached Universitario as they won the national championship. The same year saw Peru host the South American Championship. Colombia, Argentina, Bolivia and Brazil all withdrew before the competition started, so the remaining five countries, Chile, Ecuador, Paraguay, Uruguay and Peru formed a single mini-league with each team playing all the others once. Uruguay and Peru both won their first three games so when they met in the final round, the game was effectively a final. Peru won 2-1 and became South American champions.