On Sunday, 15 September 1940, Winston Churchill sat in the gallery of an underground operations room at Uxbridge, the headquarters of the RAF’s No. 11 Fighter Group. Opposite him, covering the entire wall, was a gigantic blackboard fitted with electric bulbs. Every squadron had its own column. Every row was a state: standing by at two minutes’ notice along the bottom, then readiness, available, taken off, enemy sighted, in action in red, and returning home at the top.
As German raids were reported, the bottom row began to glow and the lights climbed the wall. Then, Churchill wrote, “All were in the air. The lower line of bulbs was out. There was not one squadron left in reserve.”
He asked the group’s commander, Air Vice-Marshal Keith Park, “What other reserves have we?”
“There are none.” The case has the rest.
One glance
The board answered a question before anyone asked it. Every squadron was on it and every state had its place, so an empty bottom row could mean only one thing.
That is the whole idea of a kanban board. Put every piece of work, and the stage it has reached, where the whole team can see it. A column for each stage, a card for each job. When a card moves, the board changes, and the people looking at it see the same thing at the same time.
A busy restaurant kitchen works the same way. Order tickets go up on a rail as they come in and come down as plates go out. A cook who glances at the rail can tell how far behind the kitchen is without asking anyone.
The word itself comes from Toyota’s factories. According to the company’s official history, Toyota introduced a “supermarket method” in 1954, after reading an industry report about a Lockheed aircraft plant in the United States. Supermarkets were not yet common in Japan, and no one had personal experience of one, so the company worked out the idea from the article: the next process is the customer, and it takes only what it needs from the shelf of the process before. Adding a production instruction sheet, a kanban, “card or board” carrying the product name, number and quantity, turned that method into the kanban system.
Software teams took up the pull idea much later. In 2004, a Microsoft IT team let a new request into development only when one of a fixed number of slots opened, a limit on work in progress. By its managers’ account, the same six people went from 17 finished requests a quarter to 44 within a year.
Where the board earns its keep
Most of what a board shows is boring. Its value is in the moments when something is not: a column that keeps filling while the next one stays empty, a card that has not moved in a week, a person whose name is on six cards in “doing.”
Imagine a four-person team that handles customer requests from a shared inbox. Everyone is busy, and nobody can say where the delays come from. If the team puts each request on a board, it may find nine cards waiting in “needs sign-off” and only one in “in progress.” The slowdown might never have been in the work. It might have been in one approver’s queue, which nobody could see while it lived in an inbox.
A board shows only what is put on it, and more detail is not always more sight. After the battle, Park told Churchill that in the last twenty minutes they had been “so choked with information that we couldn’t handle it.” A board with a card for every five-minute task could turn into a wall of noise.
A board for the person watching
AI agents now keep boards of their own. In Claude Code, the task-tracking tools let Claude write down the steps of a job and move each one from pending to in progress to completed as it works.
Claude Code’s documentation adds a telling detail. Newer models “track multi-step work without a written todo list,” so those tools are off by default on them. It suggests turning them on “only when your application reads those tool calls, whether to log task activity or to render its own progress display.” Read that way, on newer models the list is mainly for the people overseeing the work, so they can see what has been done, what is happening now and what is still waiting.
The Uxbridge board did not fly a single sortie. What it gave Park and his officers was the same picture, at the same moment, of how much they had left to send.