The term [ratcatcher] appears to have been in currency at the time of the First World War. It is best defined by the characteristics that a ratcatcher may (or may not) possess.
A ratcatcher is prepared to take orders from the behavior of the enemy. They are eager to work from the boss's known objectives rather than from their last order. It helps if they have a boss who is tolerant of informed initiative and equips their subordinates to take responsibility.
To be a ratcatcher is to take risks with your (peacetime) career. But it is much harder to be a boss who nurtures ratcatchers under them. If you are minded to run your command as a jazz band (very necessary if there is any chance your communications links may be disrupted) you must educate your juniors in your doctrine and priorities, and you must lift from their shoulders the fear of making well-meaning mistakes that might be career-defining. They must know that any well-meant decision will not be seized upon as a means of thinning out the captains' list.
In July 1940, the Australian light cruiser HMAS Sydney was patrolling 100 miles away from where she had been ordered. She intercepted and sank an Italian cruiser (Battle of Cape Spada). Adm. Cunningham asked Capt. John Collins why he had been in the wrong place. He said, "Sir, I was guided by providence." Cunningham replied, "Well, you may continue to take your orders from providence." That takes a big admiral!