Believing Northern Qi to have been substantially weakened not only by Hulü's death but also by the successful campaign that Chen waged against it in 573 (capturing the provinces between the Yangtze River and the Huai River), by 575, Emperor Wu was seriously considering a major campaign against Northern Qi. However, he kept the matter secret, consulting only Yuwen Xian, Wang Yi (), and Yu Yi (). Only until he was ready in fall 575 did he announce it generally. He aimed his attack at Luoyang, but he spent about 20 days sieging it and could not capture it, and became ill. He withdrew, with virtually no gain.