If members of an organisation close ranks, they show support for each other publicly, especially when being criticised. It is a military term- when soldiers close ranks, they stand closer together so that it is difficult to pass through them.
When people cross swords, they argue or dispute. This expression is used when some groups accuse each other for non-adherence to norms. Actually no sword is used but the tempo of the argument is high enough to cause worsening of the already bad situation. It is a tussle (vehement struggle without use of arms) between the parties to establish supremacy.
This means that you shouldn't speak about things that could cause an argument or tension.This idiom was used in a classic episode of the much-loved British comedy series Fawlty Towers. As a consequence if you use this phrase in Britain, listeners will understand you to be referring to Germans, or just start laughing.
Someone who rules or controls something with a mailed fist is in absolute control and tolerates no dissent. A mailed fist in a velvet glove is used to describe someone who appears soft on the outside, but underneath is very hard.
'Iron fist' is an alternative form.