The Mishnah at the beginning of the chapter (15b) states that "thirteen prostrations" were performed in the Beis ha'Mikdash. Whenever the Kohanim would pass by one of thirteen specific places in the Beis ha'Mikdash, they would bow down. The Mishnah (16b) describes exactly where these prostrations took place. It says that they were done at the thirteen gates in the wall of the Beis ha'Mikdash (four in the north, four on the south, three in the east, and two in the west).
The Gemara says that the Mishnah follows the opinion of Aba Yosi ben Yochanan, who maintains that there were thirteen gates in the wall of the Beis ha'Mikdash. The Rabanan, however, maintain that there were only seven gates. According to the Rabanan, where were the thirteen prostrations performed? The Gemara answers that they were performed at the thirteen places where the Soreg was breached. The Mishnah in Midos (2:3) teaches that inside the wall of Har ha'Bayis stood the Soreg, a fence ten Tefachim high, which the kings of Yavan (Greece) breached in thirteen places during their war against the Jews in the times of the Chashmona'im. The Jews repaired the breaches and established an enactment that the Kohanim bow when they pass these thirteen places. The BARTENURA (Midos 2:3) adds that the prostrations at these places were instituted as a sign of gratitude to Hash-m for the victory over the Greeks.
The thirteen breaches the Greeks made in the Soreg, and the thirteen repairs that the Chashmona'im made, reflect the true essence of the battle between the Greeks and the Jews at that time.
The Midrash (Bereishis Rabah 2:4) interprets the word "darkness" in the verse, "The world was chaos and void, with darkness over the face of the deep" (Bereishis 1:2), as an allusion "to the exile imposed by the Greeks, who darkened the eyes of Yisrael with their decrees."
Why is the Greek persecution of the Jews represented by the word "darkness"?
The TUR (OC 580) teaches that on the day that the Egyptian ruler, Ptolemy, commissioned his translation of the Torah (the Septuagint), "A three-day long period of darkness descended upon the world." The translation of the Torah is the "darkness" of the Greek exile.
What was the great tragedy of the Torah being translated into another language, and why should it cause the world to become dark?
The Midrash relates that Ptolemy gathered 72 of the Jewish elders and placed them in 72 separate rooms. He did not inform any of them of the purpose of their summons. He approached each elder privately and said, "Translate [into Greek] the Torah of your teacher Moshe for me." Hash-m arranged that the same thoughts occurred to all of them, and they all made the same thirteen modifications in their translations (Sofrim 1:7-8, Megilah 9a).
When the Torah was translated into a foreign language, it lost all of the nuances of meaning. The countless allusions, exegetical derivations, and implicit insinuations in the words of the Torah, Gematriyas, acrostics, and other word-based analyses cannot be carried over from Lashon ha'Kodesh to another language. The entire body of the Oral Torah that lies beneath the surface of the written text was severed from the translation. That was the tragedy.
The Oral Torah is compared to a light that illuminates the darkness (Midrash Tanchuma, Noach #3). The Midrash says, "The Oral Torah is difficult to learn and its mastery involves great hardship. The verse therefore compares it to darkness: 'The people who walked in darkness saw a great light' (Yeshayah 9:1). The 'great light' is a reference to the great light that is seen by the Sages of the Gemara (they understand matters with great clarity), for Hash-m enlightens their eyes in matters of ritual law and laws of purity. In the future it is said of them, 'Those who love Him will shine as bright as the sun when it rises with its full intensity' (Shoftim 5:31).... Reward for the study of the Oral Torah will be received in the World to Come, as it says, 'The people who walk in darkness saw a great light.' 'Great light' is a reference to the primeval light that was hidden away by Hash-m during Creation as a reward for those who toil over the Oral Torah day and night."
Those who "shed a great light" on the Oral Torah are rewarded with the pleasure of the "great light" of Creation.
It is now clear why the translation of the Torah into Greek caused darkness to descend upon the world. The darkness was caused by the obstruction of the "great light" of the Oral Torah that resulted from the translation of the Torah into a foreign language. The Chashmona'im, who defeated the Greeks and the culture they espoused, restored to some degree the glory of the Torah to its place, and the Chanukah candles that are lit each year in commemoration of that miracle represent the "great light" of the Oral Torah.
This understanding sheds light on the significance of the thirteen breaches the Greeks made in the Soreg, and the thirteen repairs that the Chashmona'im made.
The foundation of the Oral Torah is the thirteen Midos sheha'Torah Nidreshes ba'Hen -- the thirteen exegetical principles of expounding Torah law, as enumerated in the introduction to Toras Kohanim. These principles are the basis for deriving the Oral Torah from the written text of the Torah. (This is why the Midrash ha'Zohar on Bereishis teaches that the number thirteen is a metaphor for the Oral Torah.)
The Elders made thirteen modifications in the text of the Torah when they translated it into Greek. This number represents the fact that inherent in the translation is the loss of the Oral Torah, which is derived through the thirteen exegetical principles.
The thirteen breaches made by the Greeks and repaired by the Chashmona'im represent the essence of the focus of the war of the Chashmona'im against the Greeks. The Greeks sought to eliminate the thirteen principles through their literal translation of the Torah into Greek, with its resultant loss of the Oral component of the Torah. The Chashmona'im succeeded in restoring the tools of Torah interpretation.
In order to commemorate and give thanks for the victory of authentic Torah ideology over the shallow, incomplete misrepresentation of Torah, thirteen prostrations were instituted at the sites of the repaired breaches.
It is interesting to note that according to Rashi (Devarim 33:11), there were thirteen men (twelve Chashmona'im and Elazar) who commanded the Jewish army that overthrew the Greeks. These thirteen men enabled the Jewish people to preserve the Oral Torah and its thirteen principles. (Based on the explanation of RAV DAVID COHEN in "BIRKAS YA'AVETZ," p. 147) (See also Insights to Midos 35:1.)