But that would require a 3-3 trump split, which was unlikely.

In all cases South must assume a 3-2 trump split.

In that case the 5-0 trump split would have been a positive advantage for North.

That contract would have made, thanks to the 3-2 trump split.

Everything looked easy until the lead of the heart king revealed the bad trump split.

But note that South might have survived against a bad trump split.

He wanted to guard against a 3-0 trump split, and the routine safety play was to lead low from his hand.

The game would be easy to make with a 3-2 trump split, but the 4-1 break is a nuisance.

Now South knew about the bad trump split and had problems.

A 4-3 trump split, a 62 percent chance, was virtually all South needed for success.