What are some of the defensive tactics that a target firm may employ to block a hostile takeover?

We can use these tactics to block hostile takeover like as emprove operational effeciency with cost reduced, assets revaluation, terminates overfunded pentions etc....

Most common tactic is a Poison pill coupled with a Staggered board. Other ways might include a combination of drag alongs, tag alongs, lock-up, sale of crown jewel, parachutes etc...

one of them is Stock Treasury