IOWA CITY — Years of government corruption preceded the arrests of five officials from a small northwestern Iowa city, including the mayor and police chief, according to prosecutors and a state audit.The Armstrong officials embezzled tens of thousands of dollars in public funds, falsified public records to conceal wrongdoing and used city property for personal gain, prosecutors allege in a charging document that details allegations dating to 2013.The arrests stunned the community of 900 people, which is near Iowa’s border with Minnesota and about 40 miles from the popular Okoboji vacation area in the state’s northwestern corner.Defense lawyers said they were trying to learn what prompted authorities to act against the officials now, years after some of the alleged misconduct became public in a September 2017 audit report.“It’s somewhat of an odd case.