Long story sort, The Song dynasty had two main enemies, both on their northern border. The Liao (辽) to the Northeast, and the Jin (金) to the Northwest. The Song bickered with the Liao for 150 years, and then both the Song and Liao were invaded by the Jin who took the Song capital at Kaifeng and forced them to relocate it south, to modern-day Hangzhou. The pre-invasion period is called the “Northern Song”, because the song capital was in the north, and the post-invasion period the “Southern Song”, because the capital was moved south. The way history remembers it, the Song Dynasty was corrupt and broken, which is why the Jin were able to take the capital city, and the nation only survived thanks to heroes like Yuefei.
The story of Yuefei’s tattoo is full of machismo and to-the-death loyalty, and gossip is that gangsters or military will sometimes get this same tat.
Some language stuff
We’ve got a few proper nouns, here: we’ve got the dynasty names, the Liao (辽), the Jin (金) and the Song (宋); we’ve got the name of the Song capital Kaifeng (开封), we’ve got people like Yuefei (岳飞), his mother Madam Yaotai (姚太夫人), and Deputy Marshall Zongze (副元帅宗泽).
We’ve also got some things that no longer exist, such as 醋墨, which is a mix of vinegar and ink paste used to smear on wounds to seal them. There’s also an official / military rank, 秉义郎, which I’ve translated as “Minister of Righteous Justice”, which only existed during the Song Dynasty.
And finally, we have classical-ish Chinese being used in a quote: “智勇才艺，古良将不能过”. Breaking this down word-by-word clears its meaning right up:
智 – Intelligent
勇 – brave
才 – talented
艺，- artistic
古 – antiquity
良 – Good
将 – general (military)
不能 – cannot
过 – defeat
In other words, “Even the good generals of antiquity couldn’t have defeated [someone with] so much intelligence, courage, talent and artistry.”
岳飞纹字
岳飞十五六岁时，北方的金人南侵，宋朝当权者腐败无能，节节败退，国家处在生死存亡的关头。岳飞投军抗辽。不久因父丧，退伍还乡守孝。
1126年，金兵大举入侵中原，岳飞再次投军。临行前，姚太夫人把岳飞叫到跟前，说：”现在国难当头，你有什么打算？”
“到前线杀敌，精忠报国！”
姚太夫人听了儿子的回答，十分满意，”精忠报国”正是母亲对儿子的希望。她决定把这四个字刺在儿子的背上，让他永远铭记在心。
岳飞解开上衣，露出瘦瘦的脊背，请母亲下针。
姚太夫人问：”孩子，针刺是很痛的，你怕吗？”
岳飞说：”母亲，小小钢针算不了什么，如果连针都怕，怎么去前线打仗！”
姚太夫人先在岳飞背上写了字，然后用绣花针刺了起来。但“国”字没有一点，象征国内无首。刺完之后，岳母又涂上醋墨。从此，”精忠报国”四个字就永不褪色地留在了岳飞的后背上。 母亲的鼓舞激励着岳飞。岳飞投军后，很快因作战勇敢升秉义郎。这时宋都开封被金军围困，岳飞随副元帅宗泽前去救援，多次打败金军，受到宗泽的赏识，称赞他“智勇才艺，古良将不能过”，后来成为著名的抗金英雄，受历代人民所敬仰。
