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The enlargement period of NATO since 1949

Since 1949, NATO's membership has increased from 12 to 30 countries through 8 rounds of enlargement.

  • 7
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For step three, NATO prepares additional accession protocols to the Washington Treaty. In this way, the founding agreement of the alliance is, in a sense, updated. These protocols are signed by NATO countries. For step four, the protocols must be ratified by NATO member states in line with their national laws and procedures. The approval process differs from country to country. For example, a two-thirds vote of the Senate is required for approval in the US, while a formal vote in the UK parliament is not required.