Maine military contractors, community colleges and universities, state agencies and the U.S. Navy announced Friday that they are launching a $6.5 million effort to attract and train thousands of workers to begin addressing “unprecedented workforce needs” in the state’s defense industry. The group, called the Maine Defense Industry Alliance, will establish a workforce development system and focus on recruiting, training and upgrading workers’ skills. Jobs include precision machining, welding, marine design, manufacturing and advanced manufacturing, and registered apprenticeships.