Abstract
The article distinguishes such risks for the credibility and effectiveness
of NATO as a collective defence organisation in the short and medium term
perspective, as tight defence budgets in key NATO countries, concentration
of a large part of the members of NATO on other risks than those associated
with Art. 5, the reduction of US involvement in European security connected
with permanently unequal distribution of costs in NATO and changes in
power in alliance countries that may undermine the transatlantic solidarity
in the field of security. Referring to the theory of alliances and theories of
deterrence the text argues that the credibility of alliance guarantee is always
limited and is subject to significant fluctuations over time.