Fortress Around Your Heart

The song is definitely about an ex-relationship that he would like to somehow make amends with or rekindle.

"Under the ruins of a walled city Crumbling towers and beams of yellow light"

He finds a moment -- after breakup -- after he's hurt her. The ruins of the walled city are the walls around her heart that were built up due to the pain she endured from the breakup/divorce. Crumbling towers are the remains -- after their couple 'war'. And beams of yellow light are a sense of hopefulness (at least on his part) that she's starting to soften up and could possibly let him in or forgive him. It isn't a full "open up" on her part because she's been badly hurt, but the city is starting to crumble and there HE (The Light) tries is seeping in. The yellow light is also just neutrality/friendship.

"No flags of truce, no cries of pity The siege guns had been pounding all through the night"

This is pretty simple: there's no truce yet. She's still closed off to him. (I get the sense the whole time that he's going back to see the ruins of that 'war' that he had left behind long ago). She has no pity on him. She's full on ready to shoot...

"It took a day to build the city We walked through its streets in the afternoon"

That's the beginning of the relationship. That's the place where they started...they built the "city" (love/relationship) pretty quickly. In the span of a day. Not sure if this is present or past tense when they are walking through its streets. But afternoon is a good time -- sunny -- most likely the "afternoon" of their relationship. Sort of foreshadowing that there will be a "night" as well (not as pleasant/dark).

"As I returned across the lands I'd known I recognized the fields where I'd once played I had to stop in my tracks for fear Of walking on the mines I'd laid"

So he's talking to her...he's reminiscing...remembering...or simply spending time with her. He's returning to the "lands he'd known" -- these are both the lands of the relationship and of her (this is intimate/sexual -- has a triple meaning). He recognizes the fields...again this is both speaking about the relationship and the woman. He uses "played" because he was careless with her heart, or he did something without realizing he would hurt her. He'd laid mines -- meaning: he's the one who has caused all of this destruction. He's laid mines in her heart...so at any point she could blow up at him because of the painful blows he's made to her heart. At any point he could push the wrong button, as he is with her, and change the course of things (i.e. she would no longer want to be back with him -- would get angry, tell him to leave..).

"And if I built this fortress around your heart Encircled you in trenches and barbed wire Then let me build a bridge For I cannot fill the chasm And let me set the battlements on fire"

So here it is: he wants to make amends. He is clearly taking the blame for making her so defensive and hurt (fortress around your heart), and he has made her so afraid of getting hurt (she's encircled with trenches and barbed wire-- she can do the hurting as well if anyone approaches). He now wants to build a bridge...at least be friends...or explore the possibility of getting back together. He's saying sorry in a subdued way. He cannot fill the chasm, because the damage is already done (this also has a double meaning). He wants to burn the battlements because he wants to let bygones be bygones and make a truce.

"Then I went off to fight some battle That I'd invented inside my head Away so long for years and years You probably thought or even wished that I was dead"

He's sort of "going off to war" here -- he was away. He's left her behind, for something else. Something he's invented in his head. He's fighting other battles (other women? his career? it's not clear). He is recognizing that she has either moved on or completely gotten over him in some way or another since he has been gone for so long.

"While the armies are all sleeping Beneath the tattered flag we'd made I had to stop in my track for fear Of walking on the mines I'd laid"

He's hesitating again to make and advance...he's scared that he will walk on a mine and she'll blow up and never speak to him again. Or he'll open an old wound that cannot be healed properly. The armies that are sleeping are her defenses, the flag is the truce...he's scared that she'll come to her senses again and not agree to the truce.

"And if I built this fortress around your heart Encircled you in trenches and barbed wire Then let me build a bridge For I cannot fill the chasm And let me set the battlements on fire"

"This prison has now become your home A sentence you seem prepared to pay"

He's acknowledging that she just can't let go of the past; she can't forgive him; she's still hurt. She doesn't want to make amends. She wants to live in the "prison" -- he calls it -- that he is responsible for creating around her heart. She's isolating herself and doesn't want to love or open up, for fear of losing love or being deceived/hurt. She's prepared to pay the sentence because he doesn't see her trying to get out of that 'city' of hurt. Or ...in this case...forgiving him.

"It took a day to build the city We walked through its streets in the afternoon As I returned across the lands I'd known I recognized the fields where I'd once played I had to stop in my tracks for fear Of walking on the mines I'd laid

And if I built this fortress around your heart Encircled you in trenches and barbed wire Then let me build a bridge For I cannot fill the chasm And let me set the battlements on fire"