After the Opium War , the British army pirated many history and geography collections from the Chamber , followed by thefts from local thieves ; by 1940 , the collection dwindled to less than 20,000 volumes .
After the Opium War , the British army took many history and geography collections from the library . 
 They were followed by thefts from local thieves ; by 1940 , the collection dwindled to less than 20,000 volumes .