《旧唐书·本纪·卷十六》
十月十八日，西川上奏说吐蕃侵犯雅州，朝廷命派兵前去镇守。
丁亥，西川奏吐蕃侵雅州，令发兵镇守。
On October 18, Xichuan reported that Tubo had invaded Yazhou. The imperial court ordered troops to be sent to guard it.
<s>[INST] Identify the key themes in this Classical Chinese text and explain them in English: 丁亥，西川奏吐蕃侵雅州，令发兵镇守。 [/INST] On October 18, Xichuan reported that Tubo had invaded Yazhou. The imperial court ordered troops to be sent to guard it.</s>
Identify the key themes in this Classical Chinese text and explain them in English: 丁亥，西川奏吐蕃侵雅州，令发兵镇守。
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On October 18, Xichuan reported that Tubo had invaded Yazhou. The imperial court ordered troops to be sent to guard it.
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