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
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.”