In this morning's daf yomi shiur (Yevamos daf gimel) we learn that the mishna states that 15 arayos are exempt from chalitza and yibum, etc. The reason chalitza is stated before yibum is because the mishna is going according to Abba Shaul who holds that chalitza is preferable, because any yibum done not l'shem shomayim is close to a transgression of the issur aishess ach, and the child close to being a mamzer.
Giving examples of yibum not l'shem shomayim, Rashi says for instance because she is beautiful, or would be a good wife. (Kach niray kavanaso.)
Now, that means that in the days when yibum was performed properly, the only kavana could be 'lhakem zara l'achiv', or perhaps l'shem mitzvas yibum.
But the result of the mitzvah will indeed be ishus--the yavam is expected to make a viable marriage out of a situation where he has not selected his wife by any of the criteria we ordinarily use!
L'chora what emerges is that if one is mkayem yibum lshaim shomayim, he must have complete bitachon Hashem will grant him shalom bayis, or perhaps golden middos which will allow him to form a bond with a woman who he has not chosen per se...looking forward to seeing your haaros.

These issues are resolved later in the gemara; a general statement that yibum is one of the mitzvahs that survives regardless of kavanah, save those which may have been pefromed for less than pure purposes.

Well, you have a few more pages to learn.
Azkenazic jews poskin that chalitza is preferable to yibum. Sephardic jews poskin that yibamah is preferable. So Askenazic Bet Dins are more ready to put pressure on the ybam to do chalitza than a Sephardic Bet Din. This is based on the Ramban (ad locum)who seems to indicate that the child which results from the marriage will be the reincarnation of the deceased. The last yibum in Rechovot was back in the 1950's by someone in the Temani community. I hear recently that someone did one in Bnei Brak last year.

Aryeh Shore

If someone can marry L'Shma, then they can have Shalom Bayis L'Shma too. It's those that marry for their own expectations are the ones that get the Shalom Bayis problems, since they're not getting all that they expected.

Did the Gmara leave this machloket open?
By which view did most Rishonim hold by?

Whether yibum or chalitza is preferable is a machlokes tenaim in the mishna.
I have in front of me 'Sefer Mesivta' which quotes the Shuchan Aruch and Rema.
The Shulchan Aruch brings 'stam' the opinion that yibum is preferable (shitas chachomim), and in the name of 'yesh omrim' the opinion that chalitza is preferable (shitas Abba Shaul). (I recall seeing a big debate over in the string about eruv concerning stam v'yesh halacha c'stam...here we go again.)
The Rema holds that if he is not
'lshem mitzva', and the woman doesn't want yibum, then we force him to do chalitza. (There is a line here I don't understand: he says that the minhag is that we don't force chalitza at all, but rather 'settle according to the laws of the kehila--'takanas hakehila'.)
In a footnote, Mesivta quotes Bais Shmuel that we 'force him with words' to do chalitza. In this same footnote it seems that Pischei Tshuva holds the minhag is not to do yibum, but that whem chalitza is impossible we can permit it.
I realize this post is not so satisfying--perhaps someone can do some more research and clarify the halacha.

Around the sixteenth century, the Askenazic Jews decided to stop using force in personal affairs when it was previously practiced. They stopped forcing a young man to leave town if he refuses to get married, forcing a cohen to divorce if he married a divorcee or convert and forcing chalitza. In Israel we have a number of ways to force a divorce or chalitza, the drivers licence or any other licence can be suspended and in extreme cases he can be confined in jail. As the the Sephardic follow the premise of yibum is preferred, Sephardic Bet Din tend to be reluctant to use their powers. In any event, the main outcome is extortion and needless suffering, especially for women not acquainted with Jewish law who find themselves in extreme situations.
The German Jews upto the mid 19th century, had a shtar yibum in which all the brothers signed that they would do chalitza and would not extort the poor widow. These shtarim are extant and one of my friends has one from his great, great grandfather.

Aryeh Shore

Thank you. Why did this custom stop? What do the Ashknazic batei din do?

quote:

had a shtar yibum in which all the brothers signed that they would do chalitza

At what point in a normal family upbringing would such a shtar be written and signed?

Is it each time any brother got married, a new shtar was written, signed by each brother?

Or was it only on the occasion of a married brother dying without children?

I ask because I have often wondered if there is a "priority queue" in place that any brother offering yibum takes precedence over any brother offering chalitza, subject of course to the woman's preference.

Without a priority queue, and either with or without the rabbinic MAAMER (the gift a brother willing to perform yibum sends) there seems to be an ambiguity, and whichever brother offers either option first might prevent a better offer from another brother later.

I would also like to note that I learned from an Aish tape some years ago that brothers had to have lived together in order to perform yibum.

In the case of Naomi and Ruth, which has overtones of yibum and chalitza by what did happen, I am not sure what Naomi meant by the thought that she might remarry to have another son to marry Ruth or Orpah...

She says the problem is that the young women would have to wait too long, but perhaps even then since the not yet born hypothetical younger brother would not have lived with the older brothers who had already died.

1. The oldest brother is suppose to due the yibum but if he is not available, any brother can do it, e.g. when Rabbi Ovadia was in Egypt, he had a case where the older brother was abroad, so they asked one of the younger brothers.
2. The Yibum in the story of Ruth is not Yibum in the Torah. It is apparantly a different custom. The torah was not given in a vacuum and some sort concept of pre-sinai yibum was already known to the community as we see from the story of Yehuda and Tamar. If the wife is not Jewish at the time when the husband is alive, there is no Yibum, there isn't even a marriage. If you read the text as written, Boaz does not do yibum as such. He acquires the land belonging to the decease as a "goael", a redeemer, and Ruth is sort of an auxillary property (my opinion).
3. The shtar yibum would be at each wedding. If the brother is married has no bearing as having a wife does not preclude yibum. That Askenazic Jews don't take a second wife, does not prevent the brother from extorting the widow.
4. Askenazic courts in the exile rely on public condemnation or they could put the person in Cherem, e.g. deny him an aliyah. This is not particularly effective as anyone who reads the Jewish Press would know. (Different Jewish papers tend to emphasize various topics. The Jewish Press has always given a lot of space on "Agunot" where the husband refuses to give a divorce. I think it comes from a personal experience of the editor.)

Now as to why the Askenazim stopped using force, e.g. hitting the man, I speculate that
in the case of forcing a young man to marry or leave the community, the Rabbis were unhappy when the marriage didn't work out and they got the blame. However, in general it was probably the result of emancipation as Jews felt free to leave the Ghetto and the result of conflict in the community was that people just left and became assimilated. The Nodah Biyuda (18th century) in his discussion on Cherem, says that there is no Cherem anymore. The Cherem was used when Jews had complete autonomy and by the 17th century, Jewish communities were no longer autonomous.