On 12 March 1999 three countries that had been parties to the Warsaw Treaty Organisation (WTO) and members of the Soviet-led military alliance based on this Treaty as little as 10 years ago joined the Atlantic Alliance. The first phase of NATO enlargement to the former Warsaw Treaty, and somewhat more broadly to the East, has thus been completed. It is open to question when this is going to be followed by a second wave. The experience of the first three new members from the East will thus be exclusive and decisive for at least some years to come. It is decisive not only in the political life of the three new members, but also of the Alliance. The performance of the Czech Republic, Hungary and Poland, their readiness to play along with other members of the Alliance, to contribute to extra-territorial operations, to modernise their training and equipment may be regarded important when the Alliance is to decide if and when to continue the enlargement process. Consequently, the three new members should live up to their responsibility and recognise that they can do a major disservice to the enlargement process, and more generally to the Alliance if they turn out to be troublesome allies.