This is a short, only 4 chapters, incomplete, last updated 2004 Harry Potter story. It really is not that good of a story but does have one interesting plot point (only one it's too short to have more). Hermione asks Harry that in the event they both aren't married when Voldemort declares war on the Wizarding World then they would marry one another. Are these types of pacts, marriage pacts where if the people involved can't find anyone else, common or not? I hear about them occasionally in media but I know of no one that has entered such a pact. I never really got why people would make a pact like this. If they liked one another I figure a pact wouldn't be needed and I don't like the implication it has: well if I can't find anyone better than you I'll settle for you.
Of course neither Harry or Hermione expected for Voldemort to declare war, or at least not soon, since they were expecting Voldemort to lie low for at least 10 years building up his forces. He, of course, did not. Voldemort sends a letter to Harry declaring war which I don't think Voldemort would do; he's much more likely to just attack without any declaration of intent. Voldemort signs it Tom which is something I figure he would not do since he wants to disassociate himself from his muggle parent and his pre dark lord life as much as possible.
Now they, Harry and Hermione, have to get married. The pledge was backed by magic and written in a contract by Hermione for some reason. Why Hermione would feel the need to make the pact magically binding is not explained. As happens all too often the fic is abandoned just as it was starting to become interesting. The author has a few more fics (also not updated in years) but the pairing for them are not to my liking; Hermione/Draco and Voldemort/Ginny. Voldemort with Ginny could work but only as Tom Riddle tricking her or by her being possessed. Hermione/Draco simply doesn't work going by character personalities and behavior. A young Draco, first or second year maybe, could be reformed and made to be acceptable for Hermione but the later in the series the less believable it becomes.