section_path: History/War in the Donbas (2014–2021)/Static war
section_name: Static war
paragraph_text: Static war
  
  After the Minsk agreements, there were few changes in territorial control, while the war settled into static trench warfare around the agreed line of contact, marked by artillery duels and special forces operations. Hostilities never ceased for a substantial period of time, but continued at a low level despite repeated attempts at ceasefire. Both sides began fortifying their position by building networks of trenches, bunkers and tunnels. The relatively static conflict was labelled " frozen " by some, though fighting never completely stopped. Between 2014 and 2022 there were 29 ceasefires, each agreed to remain in force indefinitely. However, none of them lasted more than two weeks.
  
  US and international officials continued to report the active presence of Russian military in eastern Ukraine, including in the Debaltseve area. In 2015, Russian separatist forces were estimated to number around 36,000 troops (compared to 34,000 Ukrainian), of whom 8,500–10,000 were Russian soldiers. Additionally, around 1,000 GRU troops were operating in the area. Another 2015 estimate held that Ukrainian forces outnumbered Russian forces 40,000 to 20,000. In 2017, on average one Ukrainian soldier died in combat every three days, with an estimated 6,000 Russian and 40,000 separatist troops in the region.
  
  The Battle of Avdiivka erupted on 29 January 2017 and lasted for several days. It saw the biggest and deadliest clashes in over a year, with more than thirty people killed and heavy artillery barrages. It began hours after newly-elected US president Donald Trump spoke by telephone with the Russian president Putin. Some in the Ukrainian government believed the Russian-backed rebels were emboldened by Trump's election. Kostiatyn Yeliseieiv, deputy head of the Ukrainian presidential administration, said it was "a test from the Russian side, of the reaction of the new American administration".
  
  In 2017, Ukraine appealed to a court of arbitration over the use of the Kerch Strait. By 2018 Russia had built a bridge over the strait, limiting the size of ships that could pass through, imposed new regulations, and repeatedly detained Ukrainian vessels. On 25 November 2018, three Ukrainian boats traveling from Odesa to Mariupol were seized by Russian warships; 24 Ukrainian sailors were detained. A day later on 26 November, the Ukrainian parliament overwhelmingly backed the imposition of martial law along Ukraine's coastal regions and those bordering Russia.
  
  More than 110 Ukrainian soldiers were killed in the conflict in 2019. In May 2019, newly elected Ukrainian President Volodymyr Zelenskyy took office promising to end the war in Donbas. In December 2019, Ukraine and pro-Russian separatists began swapping prisoners of war. Around 200 prisoners were exchanged on 29 December 2019. In December 2019 Ukraine and Russia agreed to implement a ceasefire. The two sides agreed to swap prisoners of war and disengage military forces in several regions. Russia and Ukraine could not agree on the issues of the withdrawal of Russian-backed troops and the elections in the separatist-held regions.
  
  According to Ukrainian authorities, 50 Ukrainian soldiers were killed in 2020. Between 2019 and 2021, Russia issued over 650,000 internal Russian passports to Ukrainians. There were 27 conflict-related civilian deaths in 2019, 26 deaths in 2020, and 25 deaths in 2021, over half of them from mines and unexploded ordnance.