A surprise two-pronged offensive by Ukrainian forces is reshaping the battlefield and forcing the Russians to scramble for reinforcements.

Driving the news: Ukraine launched its long-awaited push on Kherson in southern Ukraine last week, before following up with a rapid advance near Kharkiv in the northeast that seems to have caught Vladimir Putin's troops by surprise.

• A Ukrainian general said Friday that Ukraine's forces had advanced about 50km (31 miles) in three days of fighting in the region. Images spread of Ukrainian troops entering town after town, greeted by joyous residents who spent six months under occupation.
• Ukrainian President Volodymyr Zelensky hailed the "good news" but added, "now is not the time to name the settlements to which the Ukrainian flag returns."
• The surprise Ukrainian offensive seems to be aimed at cutting off the Russian forces defending Izyum, a key logistics hub for Russian operations in the north, and eventually taking the city itself, says Michael Kofman, a top expert on Russia's military at CNA.

Flashback: Kharkiv, Ukraine's second city, held out despite brutal bombardment from Russia, but smaller cities in the border region, including Izyum, quickly fell to Russia.

How it happened: The swift advance was possible because Russian positions in the area were "lightly manned or perhaps not manned at all, and the Russian military was caught by surprise," Kofman says.

• That's partly because Russia redeployed tens of thousands of troops from the east to the south ahead of the expected Ukrainian offensive there. Thus, the long-foreshadowed offensive in Kherson and the more opportunistic one in Kharkiv are linked.
• "The Ukrainian leadership clearly feels confident that they have the forces and the available reserves to sustain two offensive operations, geographically quite distant from each other," Kofman says.
• What to watch: Russia is now rushing in reinforcements, which could make it difficult for Ukraine to hold the territory it's taken and push on to Izyum.

Where it stands: The Kherson offensive appears to be proceeding more gradually than in the opening days. U.S. Under Secretary of Defense Colin Kahl on Wednesday called the Ukrainian progress there "slow but meaningful."

• Kofman anticipates Ukraine will proceed in stages over the coming weeks and months, with the ultimate goal of isolating Russian forces in Kherson city — the only regional capital to fall to Russia since the invasion.
• Both sides are attempting to train and deploy reserves after suffering heavy losses over four months of grinding warfare in the Donbas.

The other side: Russia's massive Donbas offensive has slowed almost to a halt, though Russian forces have recently captured a few towns in Donetsk.

• Still, U.S. Secretary of State Tony Blinken said Thursday during his visit to Kyiv that Putin seemed intent on continuing his war effort rather than seeking peace talks.
• At least 10 people in central Kharkiv were killed by Russian rocket attacks on Friday, a top aide to Zelensky said, claiming they were revenge for Ukraine's battlefield successes.
• Dismissing Russia's battlefield and economic setbacks, Putin declared Wednesday: “We have not lost anything, and will not lose anything." However, the tone on state TV has turned glum as Ukraine takes territory, Julia Davis reports for the Daily Beast.

What's next: The White House has warned that Russian authorities in occupied Kherson — who have already introduced the ruble, begun issuing Russian passports and instituted a Kremlin-friendly curriculum — could soon announce a sham referendum in order to claim the territory as part of Russia.

• Ukraine's offensive could complicate those plans. Analysts also believe Zelensky wants to demonstrate to his Western backers — many of whom are facing energy crises due to Russian cutbacks — that their arms and support are translating into battlefield success.