There are many positions difficult to define when it is advisable to
discontinue the trump lead. An obvious case is when the commanding
trump is against you and the lead would entail your loss of two
trumps for one card, which the adversary must make in any case. The
best play is to force the adversary to “ruff” with the high trump,
for then your trumps may make separately.
When you hold but two trumps with two against you, be careful about
taking the third round of trumps when your adversaries hold an
established suit; if the trumps are divided no doubt the lead will
save a trick; but you risk finding both trumps in one hand, in which
case the adversary will draw or force your remaining trump and make
his suit. The trump lead cannot win more than one trick and it may
lose several.
With three remaining trumps, if your suit is established, the third
round should always be taken. Should you find after one or two rounds
that the trumps are banked in one hand against you, it is, as a rule,
better to force the opponent’s hand than to continue the trump lead.
This gives you the long trump, which is no inconsiderable advantage.
The adversaries’ high trumps are sometimes placed after one round, so
that it may be advisable to discontinue the trump lead temporarily
until you can lead to better advantage from the weaker hand.
When you hold the commanding card of each side suit and do not wish
the lead of your long suit to be interrupted, it is good play to
lead the losing trump. If, however, you are not in a position to
win any card the adversary may lead, it is better play to force the
commanding trump.