The new mobilization law came into force a day after Ukraine President Volodymyr Zelenskyy signed it. Ukraine’s parliament, the Verkhovna Rada, passed it last year.

It was not immediately clear why Zelenskyy took so long to sign the measure into law. He didn’t make any public comment about it, and officials did not say how many new soldiers the country expected to gain or for which units.

Conscription has been a sensitive matter in Ukraine for many months amid a growing shortage of infantry on top of a severe ammunition shortfall that has handed Russia the battlefield initiative.

The need for a broad mobilization to beef up the number of Ukrainian troops reportedly was one of the areas of disagreement between Zelenskyy and Gen. Valerii Zaluzhnyi, the popular commander in chief of Ukraine’s armed forces whom the president replaced in February.

Russia’s own problems with manpower and planning have so far prevented it from taking full advantage of its edge.

President Vladimir Putin ordered an unpopular draft of 300,000 men in Sep. 2022 but has said there is no need for another compulsory mobilization because the numbers signing voluntary contracts are so strong.

Posters across Russian cities extol the soldiers fighting in Ukraine as patriots and heroes, and many of those signing up are attracted by salaries far higher than they can earn as civilians.

Russia, which invaded Ukraine in February 2022, has been slowly advancing in the past two months after a Ukrainian counteroffensive last year failed to make significant gains.

Defense Minister Sergei Shoigu said last month that Moscow would bolster its military by adding two new armies and 30 new formations by the end of this year.