[5] From November 2007 to August 2011, Siemoniak held the post of secretary of state in the Ministry of Interior and Administration under the leadership of successive ministers Grzegorz Schetyna and Jerzy Miller.

[8] By 2013, he oversaw Poland's biggest-ever increase in military equipment spending, with plans of investing $43 billion over the course of a decade in a procurement programme.

[10] Instead, Siemoniak called on NATO to station significant numbers of troops in eastern Europe after Russia's military intervention in Ukraine's Crimea peninsula.

[11] In 2015, he announced that Poland stood ready to assist the US should U.S. President Barack Obama decide to send arms to the Ukrainian military in its war against pro-Russian separatists.

In January 2020, Siemoniak announced his intention to run for the position as chairman of the Civic Platform, with the endorsement of outgoing leader Grzegorz Schetyna.

[15] In 2015, Siemoniak criticized the government of Beata Szydło when it replaced the head of a NATO-affiliated Counter Intelligence Centre of Excellence in Warsaw and defence ministry officials and military police staged a night-time raid on its office; he denounced the raid as "unprecedented" and "probably the first time in NATO's history that an alliance member has attacked a NATO facility.

"[16] When the Szydło government revived discussions in 2017 on whether Poland could demand reparations from Germany for the damage and loss of life it suffered during World War II, Siemoniak told reporters that while Poland does have the right to seek compensation, the government's effort was a "propaganda game" that would worsen relations with Germany and end up helping Russia.