One year after Kelsier's death Straff Venture arrives with an approximatly 50,000 men strong army before the gates of Luthadel. Two days later Lord Ashweather Cett arrives with an almost just as strong army. The Siege begins.
About 2 months later Jastes Lekal arrives with his army of about 20,000 koloss.
The two initial armies take control of the canals and cut off all incoming resources in to Luthadel. This also causes the King to forbid the citizens of Luthadel from leaving. Although forbidden to leave, citizens are able to leave though secret tunnels and passages around the city.