Defend (Minutemen)

Defend (displayed as Defend (Location Name)) is a Minutemen radiant quest in Fallout 4.

Detailed walkthrough
After joining the Minutemen, this quest can be periodically obtained when talking to Preston Garvey or listening to Radio Freedom. The Sole Survivor is informed that an allied settlement is in danger of a Super Mutant attack, and is asked to help the settlement with their defenses. This quest has an (undisclosed) 14 day time limit, so the Sole Survivor must act quickly.

To proceed with the quest you must travel to the settlement and talk to their leader, who will give you the details: a group of mutants came through earlier and caused a lot of damage, and they're afraid a bigger group is on its way. They will ask you to help build up the settlement's defenses to protect against the coming attack.

To complete the objective, you must use the settlement workshop to build defensive buildings until the settlement has a defense rating of at least 10 (the Pip-Boy will indicate your percentage toward this goal as you build). After reaching the required rating, a group of Super Mutants will spawn and begin attacking the settlement. Help eliminate the mutants (or let your settlers and defenses do it for you). Beware: if the settlement takes too much damage or the leader of the settlement is killed, the quest will fail.

With the threat neutralized, the Sole Survivor can talk to the settler from before to receive thanks and a reward of ~100 caps. If the quest was given by Preston Garvey, the Sole Survivor must report back to him to turn in the quest; it will be completed immediately upon receiving the reward otherwise.

Bugs

 * In certain locations, NPCs might spawn in inaccessible locations (for instance, Roger Warwick at Warwick Homestead might spawn inside the water cistern). This bug is shared with the other settlement quests.
 * The Warwick Homestead example can be resolved by building stairs into the cistern and a Bell outside of it. Using the bell and waiting for an in-game hour (using the Wait option) will cause the NPCs to spawn near the bell.