Explanation#1: From here there is a Kashya on Rashi in the first Perek of Kidushin, where the Gemara, commenting on the Pasuk "Vahaveisah el Toch Beisecha" states that he is not permitted to afflict her (the captive woman) during the war. Rashi explains there that he is not permitted to be intimate with her for the duration of the war, implying that even the first Bi'ah is forbidden until after all the Torah's requirements have been fulfilled.

Question#1: If that is so, David was intimate with Ma'achah only after she had converted, in which case, she was subject to marriage. That being the case, how was Tamar permitted to Amnon, seeing as she was his sister?

Question #2: And besides, we learned there in Kidushin that when the Torah permits a Y'fas Tohar, it does so in order to pacify the Yeitzer-ha'Ra, implying that the first Bi'ah takes place there and then, during the war?

Explanation #2: That is why Rabeinu Tam explains there that when the Gemara says there 'that he is not permitted to afflict her during the war', it is referring to the second Bi'ah.

Yerushalmi #1: However, the Yerushalmi cites this very point as a Machlokes between Rav and Shmuel (see Tosfos ha'Rosh).

Yerushalmi #2: In fact, this is the Lashon of the Yerushalmi (citing Shmuel) 'You said two things in the name of Rav; neither is correct. Here you said in his name that the second Bi'ah is forbidden; I say that neither the first Bi'ah nor the second Bi'ah is permitted'.

Repeat Question 1: The first Kashya that we asked on Rashi now applies to Shmuel?

Answer: It therefore appears that Tamar was not the daughter of David at all, only of Ma'achah, who was already pregnant with her when she arrived at the battlefield.

Implied Question: Then how can the Pasuk in Shmuel write about her "because the princesses would wear cloaks such as the one that she wore"?

Answer: The Navi refers to her as a princess, because she grew up as a member of David ha'Melech close family.

Clarification: 'Susim" implies (at least) two.

Text #1: 'If the Torah had written only "Sus", we would have thought that for many horses there is one La'av; Therefore it writes first "Sus" and then "Susim", to divide each one'.

Explanation: Had the Torah written "Sus" after "Lo Yarbeh lo ... ", we would have thought that the king is Chayav even on one idle horse (as is evident from the phrase "Lo Yarbeh lo Sus"). The same single La'av however, would apply even if he owned many (idle) horses. Therefore the Torah changed from "Sus" to "Susim", to make him Chayav a La'av for each and every horse.

Text #2: There are however, some erroneous texts which concludes 'to transgress an Asei and a Lo Sa'aseh (based on the fact that they interpret the question as 'Why do we need "Lo Yarbeh lo Susim" at all?'

Refutation: This is incorrect however, since "Lema'an Harbos" (which follows shortly after "Lo Yarbeh lo Susim") is not an Asei, but a clause that pertains to "ve'Lo Yashiv ha'Am Mitzraymah" which precedes it.

Explanation #1: Some commentaries explain that the writing is formed from the white, in that one fills in the empty parchment (surrounding the letter) with ink, so that the writing is formed by itself with what is now empty parchment.

Refutation #1: This is not correct however, since this is not considered 'K'sav' (writing), but 'Chok Tochos', which we have learned in Gitin, is not considered K'sav' regarding a Get and whatever is not considered K'sav' regarding a Get is not Kasher regarding a Seifer Torah either.

Refutation #2: Furthermore, why were the dignitaries of Bavel unable to read the writing on the wall (which was apparently ritten in K'sav Libuna'ah, seeing as it was no different than the K'sav that they were used to?

Explanation #2: Rabeinu Tam therefore explains that 'K'sav Libuna'ah' was the strange script used by people who resided in a place called Libnan.