Объединение войск

namespace Объединение_войск
{
    internal class Program
    {
        static void Main(string[] args)
        {
            Arena arena = new Arena();

            arena.Work();
        }
    }

    class Arena
    {
        private List<Fighter> _fighters1 = new List<Fighter>();
        private List<Fighter> _fighters2 = new List<Fighter>();

        public Arena()
        {
            _fighters1.Add(new Fighter("Иванов"));
            _fighters1.Add(new Fighter("Петров"));
            _fighters1.Add(new Fighter("Борисов"));
            _fighters1.Add(new Fighter("Баранкин"));
            _fighters1.Add(new Fighter("Сидоров"));

            _fighters2.Add(new Fighter("Антонов"));
            _fighters2.Add(new Fighter("Сергеев"));
        }

        public void Work()
        {
            Console.WriteLine("Отряд один:");

            ShowSquad(_fighters1);

            Console.WriteLine("\nОтряд два:");

            ShowSquad(_fighters2);

            UnionTeam();

            ExceptFighters();

            Console.WriteLine("\nНовый отряд два:");

            ShowSquad(_fighters2);

            Console.WriteLine("\nОтряд один:");

            ShowSquad(_fighters1);
        }

        private void UnionTeam()
        {
            char necessaryLetter = 'Б';

            _fighters2 = _fighters2.Union(_fighters1.Where(fighter => fighter.Name.StartsWith(necessaryLetter))).ToList();
        }

        private void ExceptFighters()
        {
            _fighters1 = _fighters1.Except(_fighters2).ToList();
        }

        private void ShowSquad(List<Fighter> fighters)
        {
            foreach (var fighter in fighters)
            {
                Console.WriteLine(fighter.Name);
            }
        }
    }

    class Fighter
    {
        public Fighter(string name)
        {
            Name = name;
        }

        public string Name { get; private set; }
    }
}