The failure of Nazi Germany to achieve its objectives of destroying Britain 's air defences , or forcing Britain to negotiate an armistice or an outright surrender , is considered its first major defeat and one of the crucial turning points in the war . The failure of Germany to achieve its objectives of destroying Britain 's air defences , or forcing Britain to negotiate an armistice or an outright surrender , is considered its first major defeat and one of the crucial turning points in the war .