Wash the potatoes and cook them in enough water with the caraway seeds for about 20 minutes. In the meantime, leave the bacon in a pan. Peel and dice the onion. Drain the potatoes, evaporate and let cool. Heat the broth and heat the onion cubes in it. Season the broth with mustard, vinegar, salt, pepper and sugar to taste. Peel the lukewarm potatoes and cut into slices over a suitable bowl. Mix the broth with the bacon into the potatoes. Dice the cucumbers and mix with the cucumber stock into the salad. Cover and let the salad stand for about 2 hours. Boil the eggs hard, rinse in cold water, peel and cut into thick slices. Wash and clean the radishes and cut into thin slices. Add eggs and radishes to the potato salad. Sprinkle with the chopped chives and serve. We usually eat hot wiener sausages with it.