Split Pea Soup

1 small onion, diced
1 tablespoon vegetable oil
6 cups water
1 can (14-1/2 ounces) chicken broth
1-1/2 cups dried green split peas
1 cup cubed fully cooked ham
3 bay leaves
1-1/2 teaspoons salt
1/2 teaspoon dried rosemary, crushed
1/4 teaspoon dried thyme
1/4 teaspoon pepper

In a large saucepan, saute onion in oil until tender. Add remaining ingredients. Bring to a boil. Reduce heat, cover, and simmer for 1 hour or until peas are tender. Discard bay leaves before serving.