The Three Seas Initiative (TSI) was established in 2015 as a forum for political and economic dialogue that gathers together 12 EU countries in Central and Eastern Europe (from the Baltic, Adriatic and Black Seas), with a focus on energy and infrastructure. Cooperation under the Three Seas was intended to be an additional format for regional discussion and coordination covering all the countries of Central and Eastern Europe that are EU members. As such, it was supposed to complement, not replace, other formats, such as cooperation within the Visegrad Group. Covering such a large and diverse group of countries in many respects resulted from the assumption that they all share a common denominator. It is the community of fate that caused them to face similar development challenges, including still underdeveloped infrastructure. The paradox is, in turn, that their shared history has not affected the level of integration in the region, which is still weak. This was mainly due to the lack of infrastructure connections, and therefore also economic and social ties. The process of European integration has focused investments on connections on the east-west axis, rather than north-south, which makes the latter much less communicated.

Transport, energy and digital economy were listed among the most promising areas with high added value. It should be emphasized that a large part of the projects that were identified as priorities before the Three Seas were created. This applies to, among others gas cooperation. The construction of a north-south gas corridor was planned before 2015. It was to enable gas transmission between the Polish LNG terminal in Świnoujście and the Croatian gas terminal on the island of Krk. Duplication of a large part of previously identified projects is not a disadvantage of the TSI. The new format helped to accelerate cooperation by raising the status of projects, as well as to find the necessary financing. The basic reason for the lack of sufficient infrastructure was not a deficit of concept or political will, but of funds. By establishing the Three Seas Initiative Investment Fund, the Three Seas is also to be a financial vehicle enabling the replenishment of the missing capital. Its purpose is to help attract foreign direct investment into TSI members. First success seems to be come fast. During the 56th Munich Security Conference (MSC) in Munic U.S. Secretary of State Mike Pompeo announced a commitment one bilion dollars in project defined by TSI.

It is worth emphasizing that in its intention, and this is confirmed by declarations from subsequent summits, the TSI is not only not to be the seedbed of the EU or the "Union in the Union", but on the contrary, it is to make a significant contribution to the development of the EU through the integration of areas that have been poorly integrated. Thus, the Three Seas does not have a geopolitical character understood as building an alliance having a coherent, coordinated policy towards key international actors. It rather provides a platform for pragmatic cooperation aimed at seeking added value for the widest possible range of countries of Central and Eastern Europe in individual sectors

However, it should be emphasized that the implementation of projects defined at the Three Seas summits as priorities will have significant long-term political effects. Increasing integration will naturally overlap the interests of these countries, which in the long run can consolidate the voice of the entire region and increase its position in the EU. It should be added that among the goals listed in subsequent statements from the summits, the strengthening of transatlantic ties was included, which can be seen as the great openness of the Three Seas to cooperation with the United States. This aspect is "geopolitically" important because in the era of significant tensions in EU-US relations, Central and Eastern Europe appear to be a region declaring greater closeness to Washington than Western European countries. The role of the Three Seas as a format conducive to strengthening transatlantic cooperation has been appreciated by the American administration. This can be seen in the presence of President Trump at the Three Seas Summit in Warsaw in 2017 and talks about the capital involvement of American entities in financing investments in the EEC.

Among the multilateral gas projects defined by the TSI as strategic are: 1) GIPL gas pipeline (Poland-Lithuania), 2) BRUA gas connection (Bulgaria-Romania-Hungary-Austria, 3) Eastring gas pipeline (Slovakia-Hungary-Romania-Bulgaria), 4) Romania-Hungary interconnector, 5) Baltic Pipe (Norway-Denmark-Poland and Poland-Slovakia and Poland-Ukraine gas interconnections), 6) IAP gas pipeline (Croatia, Montenegro, Albania), 8) LNG terminal on the island of KRK (Croatia). They all fit into the ideas of integrating EU gas markets. That is why they received financial support from EU funds. Project implementation would allow full integration not only of the EEC countries, but also with the well-integrated gas markets of Western European countries.

The aforesaid projects are difficult to assess from an economic point of view. Low gas consumption in the region raises a significant risk that the gas pipelines being built will not be fully used and will not be amortized. This risk meant that operators had a problem finding financing for the investment. On the other hand, the construction of connections may lead to an increase in gas demand due to its greater availability. The need to move away from coal in the EU due to energy and climate policy will create more demand for gas as an alternative energy source. In addition, thanks to the connections being built, it will be possible to freely flow gas in accordance with market signals, which will minimize the difference in gas prices in individual countries, and thus de facto lower prices in Central and Eastern Europe. Decisions from the countries in the region are driven not only by economic but also by security factors. The construction of planned gas pipelines will allow the countries of the region to achieve a satisfactory level of diversification of supplies.

It should be emphasized that the above-mentioned projects create not only synergy, but to some extent competition, which is not discussed in public debate. The subject of rivalry is the role of the transit state, which provides numerous benefits, including the revenues of the transmission system operator. The problematic issue is that at least some countries have the ambition to play such a role and therefore they promote projects that set their country as a gas hub. The main goal of Poland is gas transmission from the North Gate, which is the LNG terminal in Świnoujście and soon the Baltic Pipe gas pipeline, to the south. In this concept, Poland is a country exporting gas to Czech Republic and Slovakia. The most profitable gas corridor for the Czech Republic is the competitive one that goes through Germany via the Czech Republic to other countries of the region. Moreover, there are also differences between countries regarding the assessment of the role of Russian gas. Poland supports the minimization of the share of Russian gas in Europe, especially in the region of Central and Eastern Europe, and the Czech Republic does not see a problem in cooperation with Gazprom, especially in the era of integration of EU gas markets and high levels of supply security. The disagreement referred to the differentiated assessment of the Nord Stream 2 gas pipeline. Poland strongly criticized the project, and the Czech Republic informally supported it, seeing significant benefits in the project. However, these differences are not great enough to lead to the inhibition of gas cooperation, which is one of the most promising areas where the Three Seas can play a positive role.