The tide that did not come in

The Marines at Tarawa were put ashore on a day when the tide over the reef stayed too low for their boats, and hundreds of men had to wade five hundred metres under machine-gun fire.

The planners had been warned. It was a neap tide — the Moon at a quarter, pulling across the Sun rather than with it — and the Moon was also near apogee, about 404,000 kilometres away, which weakens it further. The two together produce the smallest tides of the month, and the atoll's reef needed the largest.