Great events can pivot on tiny details. Operation Barbarossa, the unspeakably savage Nazi invasion of the Soviet Union, launched in June, 1941, was, in part, repelled when Russia's bitter winter fell.
The oils lubricating German tanks and trucks froze before the oils used in Russian vehicles. Local knowledge and assiduous preparation prevailed. Catastrophe was averted though the cost of doing that was, in today's terms, all but unimaginable.
That great tragedy led to the establishment of today's European Union. As negotiations around Britain's withdrawal from the EU continue tiny details, far more significant than our long-standing and justified complacency towards them, all of a sudden become very significant.
Maybe not as significant as the differences between Soviet and Axis lubricating oils but in today's terms far more significant than we might care to imagine.
Bread, the Bible's staff of life, is a commodity we take for granted. However, a hard Brexit or even an agreed one may change how Irish hauliers use Britain's land bridge or continental ports and may have a negative impact on that staple's availability.
At this stage of the negotiations, and the down-to-the-wire tenor of those talks makes it likely bread will cost more, though the scale of that increase can only be guessed at today.
There are only three significant flour mills on this island, two are in Northern Ireland. Those two NI mills may soon be behind some form of a Brexit border, virtual or actual. Their produce may be subject to tariffs if it is sold into the South.
Those three mills produce - roughly - half of the flour we use each year. The rest, around 125,000 tonnes, is imported mainly via Britain's land bridge. Any interruption to that flow has consequences. Should that flour come by sea rather than via the UK industry sources anticipate a price increase of up to €30 a tonne. Today, flour costs around €400 a tonne.
There's more. Flour may be the primary ingredient in bread but all the flour in the world is useless, unless you like sourdough, without fresh yeast. All of the yeast, every last speck of it, used on this island is imported, primarily from Belgium or France.
It has a finite shelf life and cannot be warehoused for more than a few weeks. No yeast, no bread, it really is that awfully simple. Unfortunately, the flour-and-yeast dilemma is relevant to nearly all food imports and exports.
In the last few days, an agreement to allow a further month of Brexit negotiations was reached. Both sides identified reasons to hope contentious issues could be resolved.
That hope is shared on this island though a cold, pragmatic assessment is behind efforts at Rosslare Europort to open a direct, six-days-a-week ferry service to continental Europe to help hauliers avoid post-Brexit congestion on the UK landbridge, a real possibility after the December 31 cut-off date passes. Might one new link suffice? Should we, even at this 11th hour, make efforts to establish a second new service?
Just like our response to the pandemic decisions on these matters must be made despite continuing and worrying uncertainty. Even so, it would be far easier to defer plans for a second new ferry than it would be to put one in place as the land-bridge shutters come down.