Star Ship by Poul Anderson

The courtyard was filled with Khazaki warriors, standing silently in the slow heavy rain. It was the darkness of early morning, and only an occasional wan lightning flash, gleaming on spears and axes, broke the chill gloom. Anse was aware of softly-moving supple bodies pressing around him, of night-seeing eyes watching him with an impassive stare. It was he and Janazik who had the plan, and who had the most experience in warfare, and the rest looked to them for leadership. It was not easy to stand under that cool, judging scrutiny, and Anse strode forth into the street with a feeling of relief at the prospect of action.

As they moved toward the castle, along the narrow cobbled lanes winding up the hills, their army grew. Warriors came loping from alleys, came slipping out of the dark barricaded houses, seemed to rise out of the rainy night around them. All Krakenau was abroad, it seemed, but quietly, quietly.